Stock-based Compensation - Unvested RSU Activity (Details) - Restricted Stock Units (RSUs) [Member]	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Unvested RSU activity [Roll Forward]
Unvested balance beginning of period (in shares)	1,953,879
Granted (in shares)	1,694,932
Vested (in shares)	(1,027,497)
Forfeited (in shares)	(348,960)
Unvested balance end of period (in shares)	2,272,354
Unvested RSU activity, weighted average grant date fair value [Roll Forward]
Unvested balance, beginning of period (in dollars per share) | $ / shares	$ 5.46
Granted (in dollars per share) | $ / shares	3.82
Vested (in dollars per share) | $ / shares	4.66
Forfeited (in dollars per share) | $ / shares	4.51
Unvested balance, end of period (in dollars per share) | $ / shares	$ 4.74