Commitments and Contingencies - Finance Leases (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Total Payments of future minimum lease payments
Remainder of 2019	$ 11,721		$ 11,721
2020	46,284		46,284
2021	45,414		45,414
2022	33,285		33,285
2023	28,859		28,859
2024 and thereafter	63,096		63,096
Total future minimum lease payments	228,659		228,659
Less imputed lease interest	(62,294)		(62,294)
Sale of future services	83,212		83,212
Total lease liabilities	249,577		249,577
Finance lease costs
Right of use assets obtained in exchange for new finance lease liabilities	5,800	$ 0	5,900	$ 300
Restricted Cash
Restricted cash	75,900		75,900
Letter of credit	79,000		79,000
Sale Leaseback Agreements
Total Payments of future minimum lease payments
Total lease liabilities	$ 33,600		33,600		$ 81,900
Finance lease costs
Amortization of right of use asset			2,308	6,776
Interest on finance obligations			3,194	4,781
Total finance lease cost			5,502	11,557
Other information
Cash payments			$ 57,659	$ 26,392
Weighted average remaining lease term (years)	3 years 1 month 2 days	3 years 6 months 22 days	3 years 1 month 2 days	3 years 6 months 22 days
Weighted average discount rate	11.10%	11.10%	11.10%	11.10%
Finance Lease [Member]
Total Payments of future minimum lease payments
Remainder of 2019	$ 2,532		$ 2,532
2020	10,128		10,128
2021	9,276		9,276
2022	4,975		4,975
2023	3,177		3,177
2024 and thereafter	16,154		16,154
Total future minimum lease payments	46,242		46,242
Less imputed lease interest	(12,619)		(12,619)
Sale of future services	83,212		83,212
Total lease liabilities	116,835		116,835
Other Leased Property [Member]
Total Payments of future minimum lease payments
Remainder of 2019	180		180
2020	425		425
2021	407		407
2022	390		390
2023	366		366
2024 and thereafter	1,548		1,548
Total future minimum lease payments	3,316		3,316
Less imputed lease interest	(938)		(938)
Total lease liabilities	2,378		2,378
Finance obligation
Restricted Cash
Letter of credit	500		500
Finance obligation | Property and equipment
Total Payments of future minimum lease payments
Total future minimum lease payments	$ 2,400		$ 2,400