Revenue Recognition (Receivables and Deferred Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Accounts Receivable	$ 45,897	$ 37,926
Deferred Revenue (current)	52,374	35,563
Deferred Revenue (long term)	3,110	0
Increase (decrease) in current deferred revenue, net	16,811
Increase (decrease) in long-term deferred revenue, net	3,110
Deferred Revenue	55,484	35,563
Accounts Receivable [Member]
Disaggregation of Revenue [Line Items]
Accounts Receivable	38,369	30,342
Increase (decrease) in accounts receivable, net	8,027
Unbilled Receivable [Member]
Disaggregation of Revenue [Line Items]
Accounts Receivable	7,528	7,584
Increase (decrease) in unbilled receivables, net	(56)
Hosted Services - Business [Member]
Disaggregation of Revenue [Line Items]
Deferred Revenue	43,326	27,011
Hosted Services - Consumer [Member]
Disaggregation of Revenue [Line Items]
Deferred Revenue	0	0
Professional Services [Member]
Disaggregation of Revenue [Line Items]
Deferred Revenue	$ 12,158	$ 8,552