Capitalization (Details) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended		12 Months Ended	84 Months Ended
	Sep. 30, 2013	Sep. 09, 2013	Dec. 31, 2013	Dec. 31, 2013	Aug. 31, 2013	Dec. 31, 2012
Capitalization
Reverse stock split conversion ratio		5.9
Capital structure
Price of common stock issued in initial public offering (in dollars per share)	$ 22.00
Net proceeds from issuance of shares of common stock after deducting underwriters' commissions and other offering expenses (in dollars)	$ 175,600		$ 175,555	$ 175,555
Authorized shares of common stock			200,000,000	200,000,000	200,000,000	155,864,851
Authorized shares of preferred stock					5,000,000
Common stock
Capital structure
Number of shares registered in initial public offering	8,740,000
Price of common stock issued in initial public offering (in dollars per share)	$ 22.00
Net proceeds from issuance of shares of common stock after deducting underwriters' commissions and other offering expenses (in dollars)	$ 175,600
Shares issued on automatic conversion of redeemable convertible preferred stock	21,038,477