Capital Structure - Additional Information (Detail) - Common Stock [Member] - USD ($)	6 Months Ended
	Jun. 30, 2017	Nov. 30, 2016
Capital Structure [Line Items]
Repurchase of common stock, shares	(11,525,000)
Repurchase price of common stock, per share	$ 83.81
Share repurchase program, remaining authorized repurchase amount	$ 887,000,000
Share repurchase program authorized amount		$ 2,000,000,000