Employee Benefit Plan - Additional Information (Details) - 401(k) retirement savings plan - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent					50.00%	50.00%	50.00%
Participants' compensation considered for match by Employer, percent					8.00%	8.00%	8.00%
Employer contribution, amount	$ 1.4	$ 0.4	$ 4.3	$ 2.6
Employee Participant Compensation One
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent			100.00%
Participants' compensation considered for match by Employer, percent			3.00%
Employee Participant Compensation Two
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent			50.00%
Participants' compensation considered for match by Employer, percent			2.00%