Revenue Recognition (Receivables and Deferred Revenue) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($)
Contract Balances [Roll Forward]
Accounts receivable, opening balance	$ 87,620
Accounts receivable, ending balance	75,187
Contract acquisition costs noncurrent, opening balance	31,965
Contract acquisition costs noncurrent, increase (decrease), net	4,178
Contract acquisition costs noncurrent, ending balance	36,143
Deferred revenue (current), opening balance	88,751
Deferred revenue (current), increase (decrease), net	3,339
Deferred revenue (current), ending balance	92,090
Deferred revenue (long-term), opening balance	438
Deferred revenue (long-term), increase (decrease), net	2,684
Deferred revenue (long-term), ending balance	3,122
Billed receivable
Contract Balances [Roll Forward]
Accounts receivable, opening balance	70,318
Accounts receivable, increase (decrease), net	(8,222)
Accounts receivable, ending balance	62,096
Unbilled receivable
Contract Balances [Roll Forward]
Accounts receivable, opening balance	17,302
Accounts receivable, increase (decrease), net	(4,211)
Accounts receivable, ending balance	$ 13,091