Summary of Significant Accounting Policies - Comprehensive Income (Loss) (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Benefit from income taxes on realized gains on marketable securities reclassified to earnings	$ (2,757)	$ (9,318)	$ (12,291)
Provision for (benefit from) income taxes on unrealized hedging gains		(161)	161
Provision for income taxes on unrealized gains on marketable securities	$ 377	$ 831	$ 5,748