Deferred Revenue Deferred Revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 100,713	$ 110,387
Long-term deferred revenue	27,639	27,258
Deferred revenue in current liabilities	73,074	83,129
Product [Member]
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	18,974	14,274
Service [Member]
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	81,739	96,113
Government Contracts Concentration Risk [Member]
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 52,200	$ 60,300
Deferred Revenue [Member] | Non-US Government Customers [Member]
Deferred Revenue Arrangement [Line Items]
Concentration risk, percent		10.00%	10.00%