Discontinued Operations - Income (loss) from Discontinued Operations, net of tax (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income (loss) from discontinued operations, including gain on sale, net of tax	$ 102,019	$ (3,842)	$ (2,079)	$ (2,081)	$ (2,140)	$ (2,331)	$ (2,312)	$ (2,389)	$ 94,017	$ (9,172)	$ 11,062
Net income (loss) from discontinued operations	$ 102,851	$ (3,607)	$ (1,978)	$ (1,971)	$ (1,981)	$ (2,150)	$ (2,146)	$ (2,243)	95,295	(8,520)	11,316
Discontinued Operations, Disposed of by Sale
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income tax (expense) benefit											(10,100)
Gain (loss) on disposal of discontinued operation, net of tax											14,000
Discontinued Operations, Disposed of by Sale | GovDelivery
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenue									32,718	34,989	27,708
Cost of revenue									(12,069)	(11,809)	(8,121)
Selling, general, administrative and other operating expenses									(31,898)	(32,366)	(24,894)
Other non-major income and expense items									(328)	(50)	(60)
Gain on sale of discontinued operations									124,840	0	0
Total discontinued operations before income taxes, related to GovDelivery									113,263	(9,236)	(5,367)
Income tax (expense) benefit									(19,246)	64	2,403
Income (loss) from discontinued operations, including gain on sale, net of tax									94,017	(9,172)	(2,964)
Less: discontinued operations attributable to noncontrolling interests									(1,278)	(652)	(254)
Net income (loss) from discontinued operations									95,295	$ (8,520)	$ (2,710)
Gain (loss) on disposal of discontinued operation, net of tax									$ 11,100