Income Taxes - Change in Liability for Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 12	$ 6
Increase for other tax positions of prior years	10	7
Increase from Acquisitions	33	0
Decrease related to tax positions taken in prior years	(2)	(1)
Balance at end of year	$ 53	$ 12