Summary of Significant Accounting Policies - Recently Adopted Accounting Standards (Details) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jan. 01, 2018 USD ($)	Jan. 01, 2017 USD ($)
Income tax benefit	$ (6,500)	$ (2,000)	$ (45,012)	$ (444)	$ 1,491	$ 7,862	$ 3,887	$ 4,441	$ 1,132	$ (45,965)	$ 17,322	$ (29,656)
Retained Earnings (Accumulated Deficit)		486,957				536,350				486,957	536,350
Increase in deferred tax assets		4,902				38,688				4,902	38,688
Additional paid-in capital		$ 250,216				$ 248,748				$ 250,216	$ 248,748
ASU 2016-09
Number of key accounting changes affect the timing of revenue recognition | item										2
Income tax benefit										$ 1,300
Retained Earnings (Accumulated Deficit)														$ (600)
Increase in deferred tax assets														300
Additional paid-in capital														$ 900
ASU 2014-09
Retained Earnings (Accumulated Deficit)													$ (40)