Employee Savings Plan and Employee Stock Purchase Plan - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	May. 05, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Contribution Plan Disclosure [Line Items]
401(k) eligibility minimum service period				90 days
401(k) description of plan contributions				Contribution equal to 100% of the first 1% of salary deferrals and 50% of salary deferrals between 2% and 6%, up to a maximum matching contribution of 3.5% of salary each plan year for our employees.
Employee vested percentage in salary deferrals and roll over contributions				100.00%
Minimum period for vesting 100% contributions				2 years
Minimum period for vesting of discretionary contributions				2 years
Matching contribution amount		$ 0.6	$ 0.4	$ 1.8	$ 1.3
Employee Stock Purchase Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Employees Company's common stock shares purchase limit percentage	10.00%
Purchase of shares of common stock		24,935
Compensation expense related to ESPP		$ 0.1		$ 0.2
Share of common stock purchase maximum				2,000,000
Maximum number of shares that may be acquired by a participant				2,000
After Two Years Of Employment [Member]
Defined Contribution Plan Disclosure [Line Items]
Matching contributions, vesting percentage				100.00%
One Hundred Percent Match For Percent Of Participants Contribution [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contribution percentage				100.00%
Percentage of salary deferrals				1.00%
50% Matching Contribution [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer contribution percentage				50.00%
Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
401(k) eligible age of employee				21 years
Minimum [Member] | 50% Matching Contribution [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of salary deferrals				2.00%
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of salary deferrals				3.50%
Maximum [Member] | Employee Stock Purchase Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Purchase price of common stock expressed as a percentage of its fair market value	85.00%
Maximum [Member] | 50% Matching Contribution [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of salary deferrals				6.00%