Business - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Jan. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Jan. 30, 2014	Dec. 31, 2012
Accounting Policies [Abstract]
Date of formation	Jul. 02, 2004
Common stock, shares issued			22,778,597		22,778,597		4,288,243	5,750,000
Common stock, shares issued upon exercise by underwriters								750,000
Public offering price			$ 11.00		$ 11.00			$ 11.00
Aggregate gross offering proceeds		$ 63,250
Net proceeds as a result of IPO		56,247			57,762
Underwriting discounts and commissions		4,427
Additional offering expenses paid or accrued	2,576
Net proceeds from equity financing and issuance of debt prior to the IPO							73,309
Unrestricted cash and cash equivalents			58,393	17,733	58,393	17,733	12,357		1,117
Accumulated deficit			(76,029)		(76,029)		(62,456)
Net cash (used in) provided by operating activities					(11,818)	7,893
Net loss			$ (6,545)	$ (4,575)	$ (13,573)	$ (1,870)