Leases - Components of lease expense, and lease assets and liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Lease Cost
Amortization of right-to-use assets (included in depreciation expense)	$ 177	$ 178	$ 532	$ 534
Interest on lease liabilities	102	135	329	422
Operating lease cost	3,936	4,181	12,074	12,861
Short-term lease cost	105	131	483	452
Variable lease cost	406	595	1,322	1,391
Total lease cost	4,726	$ 5,220	14,740	15,660
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from finance lease			354	444
Operating cash flows from operating leases			11,798	11,142
Financing cash flows from finance lease			980	864
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability			16,470	$ 15,282
Assets and Liabilities, Lessee [Abstract]
Finance lease right-of-assets (included in other assets)	$ 1,778		$ 1,778		$ 2,311
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other assets, net		Other assets, net
Operating lease right-of-use assets	$ 82,849		$ 82,849		76,859
Finance lease liability, current (included in current installments of long-term debt)	$ 1,457		$ 1,457		1,325
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)	$ 2,543		$ 2,543		3,654
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)	$ 11,466		$ 11,466		11,043
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Liabilities, Current		Other Liabilities, Current
Operating lease liability, noncurrent	$ 74,407		$ 74,407		$ 67,898
Weighted average remaining lease term finance leases	2 years 9 months 18 days		2 years 9 months 18 days		3 years 6 months
Weighted average remaining lease term operating leases	10 years 1 month 6 days		10 years 1 month 6 days		10 years 2 months 12 days
Weighted average discount rate finance leases	10.10%		10.10%		10.10%
Weighted average discount rate operating leases	4.40%		4.40%		4.70%