Revenue Recognition (Receivables and Deferred Revenue) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)
Contract Balances [Roll Forward]
Opening balance, Receivable	$ 37,926
Ending balance, Receivable	51,727
Opening balance, Deferred Revenue (current)	35,563
Increase (decrease) in current deferred revenue, net	20,554
Ending balance, Deferred Revenue (current)	56,117
Opening balance, Deferred Revenue (long-term)	0
Increase (decrease) in long-term deferred revenue, net	2,067
Ending balance, Deferred Revenue (long-term)	2,067
Accounts Receivable
Contract Balances [Roll Forward]
Opening balance, Receivable	30,342
Increase (decrease) in accounts receivable, net	10,300
Ending balance, Receivable	40,642
Unbilled Receivable
Contract Balances [Roll Forward]
Opening balance, Receivable	7,584
Increase (decrease) in unbilled receivables, net	3,501
Ending balance, Receivable	11,085
Hosted Services - Business
Contract Balances [Roll Forward]
Opening balance, Deferred Revenue (current)	27,011
Ending balance, Deferred Revenue (current)	45,225
Opening balance, Deferred Revenue (long-term)	0
Ending balance, Deferred Revenue (long-term)	1,653
Professional Services
Contract Balances [Roll Forward]
Opening balance, Deferred Revenue (current)	8,552
Ending balance, Deferred Revenue (current)	10,892
Opening balance, Deferred Revenue (long-term)	0
Ending balance, Deferred Revenue (long-term)	$ 414