Income Taxes (Components of Income Tax Expense) (Detail) - USD ($) $ in Millions	3 Months Ended								6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current income tax expense
U.S. federal											$ 179	$ (251)	$ 132
U.S. State and local											49	(12)	20
Non-U.S.											349	306	261
Total current income tax											577	43	413
Deferred income tax expense
U.S. federal											107	173	31
U.S. State and local											(16)	(10)	6
Non-U.S.											(53)	8	(37)
Deferred Income Tax Expense (Benefit)				$ 6					$ (40)	$ (53)	38	171	0
Total	$ 224	$ 124	$ 157	$ 110	$ 40	$ (220)	$ 285	$ 109	$ 267	$ 391	$ 615	$ 214	$ 413