Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Jan. 01, 2017
Income Taxes [Abstract]
Income tax benefit (expense)	$ (48)	$ 3,179	$ (73)	$ 3,151
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	15	$ 520	71	520	$ 899
Cumulative Effect of Change on Equity or Net Assets						$ 136
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount				$ 3,300
Unrecognized Tax Benefits	$ 170		$ 170		$ 172