Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	$ 4	$ 7
Unrecognized Tax Benefits, Period Increase (Decrease)	$ (3)	$ 1	$ 2
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%	35.00%
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 446	$ 332	$ 332
Effective Income Tax Rate Reconciliation, Percent	35.00%	128.00%	17.00%
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 348	$ 352	$ 364
Additions for current year tax positions	2	0	2
Additions for tax positions of prior years	146	2	1
Reductions for tax positions of prior years	(26)	(5)	(1)
Settlements	0	0	(13)
Lapse of statute of limitations	(7)	(1)	(1)
Ending balance	463	348	352
Unrecognized Tax Benefits, Income Tax Penalties Accrued	0	0
Unrecognized Tax Benefits, Income Tax Penalties Expense	$ 0	$ 0	$ 0
UNITED STATES
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 161