Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	1 Months Ended
	Sep. 22, 2014	Sep. 30, 2014	Mar. 31, 2015	Dec. 31, 2014
Summary Of Significant Accounting Policies [Line Items]
Number of common shares issued on conversion of redeemable convertible preferred stock	14,860,173	14,860,173
Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash equivalents			$ 94,162	$ 105,256