Revenues - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Contract with customer, asset, gross	$ 34,300	$ 34,300	$ 11,300
Contract with customer, liability	136,500	136,500	71,100
Contract with customer, liability, revenue recognized	1,100	(241,510)
Other current assets	118,085	118,085	81,604
Unearned revenue			77,000	$ 114,300
Unearned revenue	93,621	93,621	41,438
Retained earnings (accumulated deficit)	(425,396)	(425,396)	(337,873)
Accounting Standards Update 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Total revenues		(25,900)
Other current assets	(21,000)	(21,000)
Unearned revenue	22,200	22,200
Unearned revenue	8,900	8,900
Retained earnings (accumulated deficit)	$ (36,700)	$ (36,700)	$ (10,900)