Common Stock - Additional Information (Detail) - USD ($)			12 Months Ended
	Nov. 14, 2016	Oct. 30, 2014	Dec. 31, 2016
2014 Repurchase Program
Common Stock Disclosure [Line Items]
Common stock, repurchases authorized		$ 500,000,000
Stock repurchase program completion date		2016-11
Common stock, repurchased during the period			$ 194,500,000
2016 Repurchase Program
Common Stock Disclosure [Line Items]
Common stock, repurchases authorized	$ 1,000,000,000
Stock repurchase program expiration date	Dec. 31, 2019
Common stock, repurchased during the period			$ 61,700,000