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Long-Term Debt and Interest Rate Swap Arrangements (Narrative) (Details) (USD $)
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3 Months Ended | 12 Months Ended | 3 Months Ended | 3 Months Ended | |||||||||||||||||||||
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Mar. 31, 2013
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Mar. 31, 2012
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Sep. 02, 2010
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Mar. 31, 2013
7.125% Senior Secured Notes due 2017
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Dec. 31, 2012
7.125% Senior Secured Notes due 2017
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Dec. 31, 2011
7.125% Senior Secured Notes due 2017
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Mar. 23, 2010
7.125% Senior Secured Notes due 2017
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Mar. 31, 2013
7.5% Senior Secured Notes due 2019, net of original issue discount
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Dec. 31, 2012
7.5% Senior Secured Notes due 2019, net of original issue discount
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Dec. 31, 2011
7.5% Senior Secured Notes due 2019, net of original issue discount
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Sep. 25, 2009
7.5% Senior Secured Notes due 2019, net of original issue discount
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Mar. 31, 2013
7.375% Senior Secured Notes due 2020
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Dec. 31, 2012
7.375% Senior Secured Notes due 2020
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Dec. 31, 2011
7.375% Senior Secured Notes due 2020
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Mar. 23, 2010
7.375% Senior Secured Notes due 2020
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Mar. 31, 2013
5.125% Senior Secured Notes due 2022
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Dec. 31, 2012
5.125% Senior Secured Notes due 2022
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Jul. 02, 2012
5.125% Senior Secured Notes due 2022
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Mar. 31, 2013
4.375% Senior Secured Notes due 2023, net of original issue discount
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Dec. 31, 2012
4.375% Senior Secured Notes due 2023, net of original issue discount
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Mar. 31, 2013
5.95% Senior Secured Notes due 2043, net of original issue discount
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Dec. 31, 2012
5.95% Senior Secured Notes due 2043, net of original issue discount
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| Debt Instrument [Line Items] | |||||||||||||||||||||||||
| Line of credit facility maximum borrowing capacity | $ 2,000,000,000 | $ 2,000,000,000 | |||||||||||||||||||||||
| Line of credit facility standby letter of credit | 250,000,000 | 250,000,000 | |||||||||||||||||||||||
| Line of credit facility, uncommitted loan | 1,000,000,000 | ||||||||||||||||||||||||
| Debt instrument lower range of basis spread on variable rate | 0.25% | 0.50% | |||||||||||||||||||||||
| Debt instrument higher range of basis spread on variable rate | 2.00% | 3.00% | |||||||||||||||||||||||
| Line of credit facility remaining borrowing capacity | 1,700,000,000 | 1,100,000,000 | |||||||||||||||||||||||
| Line of credit facility interest rate at period end | 1.70% | ||||||||||||||||||||||||
| Principal amount of tender offer | 500,000,000 | 250,000,000 | |||||||||||||||||||||||
| Debt instrument interest rate stated percentage | 7.125% | 7.125% | 7.50% | 7.50% | 7.375% | 7.375% | 5.125% | 5.125% | 4.375% | 5.95% | |||||||||||||||
| Repurchase price of individual bonds including premium | 1,039.40 | 1,120 | |||||||||||||||||||||||
| Face value of individual bonds repurchased | 1,000 | 1,000 | |||||||||||||||||||||||
| Extinguishment of debt amount | 124,000,000 | 231,000,000 | |||||||||||||||||||||||
| Extinguishment of debt, subsequent event | 376,000,000 | ||||||||||||||||||||||||
| Debt and capital lease obligations | 3,596,000,000 | 3,477,000,000 | 2,490,000,000 | 376,000,000 | 500,000,000 | 500,000,000 | 500,000,000 | 760,000,000 | 988,000,000 | 986,000,000 | 1,000,000,000 | 500,000,000 | 500,000,000 | 500,000,000 | 500,000,000 | 500,000,000 | 500,000,000 | 500,000,000 | 750,000,000 | 0 | 300,000,000 | 0 | |||
| Debt issuance price percentage | 98.278% | 99.968% | 99.973% | ||||||||||||||||||||||
| Loss on extinguishment of debt | (41,000,000) | 0 | 22,000,000 | ||||||||||||||||||||||
| Notional amount of interest rate derivative instruments not designated as hedging instruments | 3,100,000,000 | ||||||||||||||||||||||||
| Gain on financial instruments | 12,000,000 | 11,000,000 | 48,000,000 | 50,000,000 | 40,000,000 | ||||||||||||||||||||
| Interest rate derivatives at fair value net | 12,000,000 | 59,000,000 | |||||||||||||||||||||||
| Interest rate derivative liabilities at fair value | 13,000,000 | 61,000,000 | |||||||||||||||||||||||
| Interest rate derivative assets at fair value | $ 1,000,000 | $ 2,000,000 | |||||||||||||||||||||||
| Debt weighted average interest rate | 5.80% | 7.00% | |||||||||||||||||||||||