Debt - Convertible Notes (Details) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended
	Feb. 29, 2016 USD ($) $ / shares shares	Jan. 31, 2016 $ / shares shares	May 31, 2015 USD ($) item $ / shares	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Apr. 30, 2013 USD ($)
Convertible Notes
Common stock issued upon conversion of notes (in shares) | shares	1,839,080	1,839,080
Conversion of debt into equity	$ 20,000
Amount of debt converted					$ 20,000
Conversion price (in dollars per share) | $ / shares		$ 10.875
Interest expense				$ 61,138	$ 69,428
Convertible notes voting restriction period				3 years
2013 Convertible Notes
Convertible Notes
Amount of debt issued						$ 20,000
Conversion price (in dollars per share) | $ / shares	$ 10.875
Gain (loss) on conversion of notes to common stock				$ 0
2015 Convertible Notes
Convertible Notes
Amount of debt issued			$ 25,000
Transaction costs			$ 50
Conversion price (in dollars per share) | $ / shares			$ 21.50
Conditional conversion price (in dollars per share) | $ / shares			$ 30.10
Number of trading days for which stock price must exceed specified price | item			20
Number of consecutive trading days during which stock price must exceed specified price			30 days
Interest rate of debt (as a percent)			7.50%