Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Disclosure Income Taxes Narrative [Abstract]
Effective tax rate	37.80%	37.30%	36.60%	36.90%
Excess tax benefit (deficiency) [discrete item]	$ (2)		$ 6