Leases - Components of lease expense, and lease assets and liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Lease Cost
Amortization of right-to-use assets (included in depreciation expense)	$ 178	$ 356
Interest on lease liabilities	141	287
Operating lease cost	4,232	8,680
Short-term lease cost	121	321
Variable lease cost	371	737
Total lease cost	5,043	10,381
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from finance lease		303
Operating cash flows from operating leases		7,447
Financing cash flows from finance lease		566
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		15,206
Assets and Liabilities, Lessee [Abstract]
Finance lease right-of-assets (included in other assets)	$ 2,667	$ 2,667
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other, net	Other, net
Operating lease right-of-use assets	$ 83,985	$ 83,985	$ 0
Finance liability, current (included in current installments of long-term debt)	$ 1,244	$ 1,244
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Long Term Debt And Capital Lease Obligations Current	Long Term Debt And Capital Lease Obligations Current
Finance lease liability, noncurrent (included in long-term debt)	$ 4,338	$ 4,338
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long Term Debt And Capital Lease Obligations	Long Term Debt And Capital Lease Obligations
Operating lease liability, current (included in other accrued liabilities)	$ 11,737	$ 11,737
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Liabilities, Current	Other Liabilities, Current
Operating lease liability, noncurrent	$ 73,878	$ 73,878	$ 0
Weighted average remaining lease term finance leases	3 years 9 months 18 days	3 years 9 months 18 days
Weighted average remaining lease term operating leases	10 years 3 months 18 days	10 years 3 months 18 days
Weighted average discount rate finance leases	10.10%	10.10%
Weighted average discount rate operating leases	4.70%	4.70%