Common Stock - Share Repurchase of Common Stock (Detail) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended			264 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Statement Of Stockholders Equity [Abstract]
Aggregate purchase price	$ 431,367	$ 567,544	$ 554,491	$ 6,307,000
Number of shares repurchased	290	508	581	24,100