Leases - Lease Cost, Weighted Average Term, Discount Rates and Cash Flows (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Lease cost:
Operating lease cost	$ 6,411	$ 12,278
Finance lease cost:
Amortization of right-of-use assets	20,577	41,242
Interest on lease liabilities	5,770	11,788
Short-term lease cost	156	276
Variable lease cost	1,422	3,392
Total lease cost	$ 34,336	$ 68,976
Weighted average remaining lease term (in years):
Finance leases	4 years 4 months 6 days	4 years 4 months 6 days
Operating leases	10 years 1 month 28 days	10 years 1 month 28 days
Weighted average discount rate:
Finance leases	10.77%	10.77%
Operating leases	6.18%	6.18%
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 6,046	$ 11,417
Operating cash flows from finance leases	5,770	11,788
Financing cash flows from finance leases	10,022	19,780
Right-of-use asset obtained in exchange for lease liability	$ 0	$ 1,000