Income Taxes - Schedule of Reconciliation of Change in Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Accrued interest and penalties expense (benefit) related to income taxes included in income tax expense	$ (5)	$ (3)	$ (3)
Gross Unrecognized Tax Benefits
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	130	107	114
Additions for tax positions related to prior years	0	38	9
Reductions for tax positions related to prior years due to IRS and other settlements	(45)	(15)	(16)
Ending balance	85	130	107
Portion of balance at December 31, that, if recognized, would impact the effective income tax rate	55
Accrued Interest and Penalties
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	33	36	39
Additions for tax positions related to prior years	6	8	2
Reductions for tax positions related to prior years due to IRS and other settlements	(15)	(11)	(5)
Ending balance	24	33	36
Portion of balance at December 31, that, if recognized, would impact the effective income tax rate	16
Gross Tax, Interest and Penalties
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	163	143	153
Additions for tax positions related to prior years	6	46	11
Reductions for tax positions related to prior years due to IRS and other settlements	(60)	(26)	(21)
Ending balance	109	$ 163	$ 143
Portion of balance at December 31, that, if recognized, would impact the effective income tax rate	$ 71