Discontinued Operations - Assets and Liabilities from Discontinued Operations (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Carrying amounts of major classes of assets included as part of discontinued operations
Cash and cash equivalents	$ 27,982	$ 20,834	$ 14,495	$ 21,961
GovDelivery | Disposed of by sale
Carrying amounts of major classes of assets included as part of discontinued operations
Cash and cash equivalents	27,982	20,834
Accounts receivables, net of allowance	18,446	1,648
Fixed assets, net of accumulated depreciation and amortization	4,513	5,266
Goodwill	231,424	231,787
Intangible assets, net	60,121	72,706
Other assets included in the disposal group	6,714	26,281
Total assets of discontinued operations	349,200	358,522
Carrying amounts of major classes of liabilities included as part of discontinued operations
Accounts payable	12,670	11,161
Accrued expenses	7,572	8,415
Accrued compensation and benefits	6,566	7,671
Deferred revenue	37,081	36,824
Other liabilities included in the disposal group	9,749	14,753
Total liabilities of discontinued operations	$ 73,638	$ 78,824