Accounting for Shared-Based Payments - Stock option (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 08, 2015	Jan. 17, 2013	Nov. 30, 2011
Shared-based payments
Total stock-based compensation expense (in dollars)	$ 9,724	$ 4,722	$ 4,614
Research and development
Shared-based payments
Total stock-based compensation expense (in dollars)	2,452	1,914	1,465
Selling, general and administrative
Shared-based payments
Total stock-based compensation expense (in dollars)	$ 7,272	2,808	$ 3,149
2008 Equity Compensation Incentive Plan
Shared-based payments
Number of shares reserved under the plan				30,000,000	15,000,000	7,500,000
Stock option outstanding	18,869,771
Stock option available for future issuance	11,130,229
2009 Directors Option Plan
Shared-based payments
Stock option outstanding	323,500
Stock option available for future issuance	176,500
Stock options
Shared-based payments
Vesting period	3 years
Contractual term	10 years
Unrecognized compensation cost related to non-vested employee stock options, net of expected forfeitures (in dollars)	$ 17,600	$ 9,100
Weighted-average remaining vesting period over which unrecognized compensation cost is to be recognized	2 years 2 months 1 day	2 years
Number of stock options which vest upon a change of control (in shares)	2,159,500	2,159,500
Weighted-average assumptions used to estimate fair value of stock option awards using the Black-Scholes option valuation model
Risk-free interest rate, minimum (as a percent)	1.46%	1.78%	0.66%
Risk-free interest rate, maximum (as a percent)	2.02%	2.30%	2.75%
Expected volatility, minimum (as a percent)	50.00%	52.00%
Expected volatility, maximum (as a percent)	80.00%	60.00%
Expected volatility (as a percent)			60.00%
Expected term	6 years	6 years	6 years
Weighted-average fair value of all options granted (in dollars per share)	$ 3.79	$ 1.98	$ 2.68