Leases (Finance And Operating Lease Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finance Lease, Cost1 [Abstract]
Amortization of right-of-use assets	$ 1,652	$ 2,413	$ 0
Interest on lease liabilities	501	518
Total finance lease cost	2,153	2,931
Operating Lease, Cost [Abstract]
Fixed lease cost	12,057	12,556
Short-term lease cost	824	830
Variable lease cost	1,926	1,986
Sublease income	(2,579)	(1,857)
Total operating lease cost	12,228	13,515
Cost of revenues
Finance Lease, Cost1 [Abstract]
Amortization of right-of-use assets	1,212	1,771
Operating Lease, Cost [Abstract]
Total operating lease cost	3,532	3,885
Selling and marketing
Finance Lease, Cost1 [Abstract]
Amortization of right-of-use assets	176	258
Operating Lease, Cost [Abstract]
Total operating lease cost	4,009	4,192
Research and development
Finance Lease, Cost1 [Abstract]
Amortization of right-of-use assets	175	253
Operating Lease, Cost [Abstract]
Total operating lease cost	2,609	2,595
General and administrative
Finance Lease, Cost1 [Abstract]
Amortization of right-of-use assets	89	131
Operating Lease, Cost [Abstract]
Total operating lease cost	$ 2,078	$ 2,843