Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Value of shares authorized to repurchase program	$ 750,000,000	$ 1,100,000,000
Shares repurchased	4,700	20,300
Average price per share for common shares repurchased	$ 78.39	$ 80.45
Total cost of common shares repurchased	$ 371,000,000	$ 1,636,000,000	$ 316,000,000
Remaining capacity for authorized repurchase shares	458,000,000
Dividends paid	$ 255,000,000	$ 735,000,000
Dividends paid per share	$ 1.50	$ 4.00
Dividends record date	Mar. 31, 2016
Quarterly cash dividend per share		1.40
Special dividend per share		$ 2.60
Partners capital account units, Redeemed	54
Partners capital account, Redemption value	$ 4,000,000