Income Taxes - Rollforward of Total Gross Unrecognized Tax Benefit (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefit as of beginning of period	$ 15,472	$ 10,961	$ 5,929
Tax positions related to current year, additions for uncertain tax positions	5,087	4,133	2,742
Tax positions related to prior year, additions for uncertain tax positions	80	378	2,290
Unrecognized tax benefit as of end of period	$ 20,639	$ 15,472	$ 10,961