Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Non Variable Interest Entities [Line Items]
Deferred income taxes, net	$ 0	$ 970
Valuation allowance	1,236	7
Valuation Allowance Deferred Tax Asset Change In Amount	1,200
NOL carryforward	2,800
Foreign tax credit	62	7
Alternative minimum tax credit carryforward	$ 30	$ 26