Leases (Lease Expense and Cash Outflows from Operating and Finance Leases) (Details) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Leases [Abstract]
Operating lease cost	$ 9,475	$ 9,707	$ 28,255	$ 28,212
Short-term lease cost	218	397	1,007	910
Variable lease cost	663	715	1,818	2,405
Amortization	17	67	94	186
Interest on lease liabilities	4	5	11	12
Total lease cost	$ 10,377	$ 10,891	31,185	31,725
Cash paid for amounts included in measurement of lease liabilities:
Operating cash flows from operating leases			19,376	28,023
Operating cash flows from finance leases			11	12
Financing cash flows from finance leases			86	182
Right-of-use assets obtained in exchange for lease obligations:
Operating leases			13,711	32,511
Finance leases			$ 60	$ 159