Annual report pursuant to Section 13 and 15(d)

Income Taxes Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details)

v3.8.0.1
Income Taxes Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details)
$ in Millions
12 Months Ended
Dec. 31, 2017
USD ($)
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]  
Balance at January 1, 2017 $ 55
Increases related to prior year tax positions 1
Decreases related to prior year tax positions (8)
Decreases related to settlements with taxing authorities (4)
Increases related to current year tax positions 6
Balance at December 31, 2017 $ 50