Schedule II - Valuation and Qualifying Accounts (Detail) (Valuation Allowances for Deferred Tax Assets [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Valuation Allowances for Deferred Tax Assets [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 23,964	$ 14,852	$ 9,681
Additions/charged to expense	12,681	9,112	5,171
Balance at end of period	$ 36,645	$ 23,964	$ 14,852