Acquisitions (Assets Acquired and Liabilities Assumed and Divested) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jun. 28, 2018	Mar. 21, 2018	Dec. 31, 2017	Nov. 16, 2017	Jul. 12, 2017	Apr. 21, 2017	Jan. 10, 2017
Assets Acquired
Goodwill	$ 157,389			$ 154,607
RO Innovation, Inc. [Member]
Assets Acquired
Cash		$ 1,427
Accounts receivable		1,807
Other current assets		22
Property and equipment		51
Goodwill		3,170
Other assets		0
Total assets acquired		16,774
Liabilities Assumed
Accounts payable		(232)
Accrued expense and other		(679)
Deferred tax liabilities		0
Deferred revenue		(1,613)
Total liabilities assumed		(2,524)
Total consideration		14,250
RO Innovation, Inc. [Member] | Customer Relationships [Member]
Assets Acquired
Intangible assets		8,596
RO Innovation, Inc. [Member] | Trade Name [Member]
Assets Acquired
Intangible assets		65
RO Innovation, Inc. [Member] | Technology [Member]
Assets Acquired
Intangible assets		$ 1,636
Interfax Communications Limited [Member]
Assets Acquired
Cash			$ 2,675
Accounts receivable			1,713
Other current assets			0
Property and equipment			286
Goodwill			16,141
Other assets			14
Total assets acquired			46,920
Liabilities Assumed
Accounts payable			(737)
Accrued expense and other			(3,122)
Deferred tax liabilities			(3,061)
Deferred revenue			0
Total liabilities assumed			(6,920)
Total consideration			40,000
Interfax Communications Limited [Member] | Customer Relationships [Member]
Assets Acquired
Intangible assets			21,093
Interfax Communications Limited [Member] | Trade Name [Member]
Assets Acquired
Intangible assets			638
Interfax Communications Limited [Member] | Technology [Member]
Assets Acquired
Intangible assets			$ 4,360
Qvidian Corporation [Member]
Assets Acquired
Cash					$ 468
Accounts receivable					1,907
Other current assets					334
Property and equipment					108
Goodwill					21,225
Other assets					8
Total assets acquired					60,176
Liabilities Assumed
Accounts payable					(388)
Accrued expense and other					(399)
Deferred tax liabilities					0
Deferred revenue					(9,389)
Total liabilities assumed					(10,176)
Total consideration					50,000
Qvidian Corporation [Member] | Customer Relationships [Member]
Assets Acquired
Intangible assets					30,160
Qvidian Corporation [Member] | Trade Name [Member]
Assets Acquired
Intangible assets					227
Qvidian Corporation [Member] | Technology [Member]
Assets Acquired
Intangible assets					$ 5,739
Waterfall International Inc. [Member]
Assets Acquired
Cash						$ 100
Accounts receivable						1,477
Other current assets						608
Property and equipment						23
Goodwill						18,575
Other assets						0
Total assets acquired						30,093
Liabilities Assumed
Accounts payable						(605)
Accrued expense and other						(1,136)
Deferred tax liabilities						0
Deferred revenue						(1,220)
Total liabilities assumed						(2,961)
Total consideration						27,132
Waterfall International Inc. [Member] | Customer Relationships [Member]
Assets Acquired
Intangible assets						6,400
Waterfall International Inc. [Member] | Trade Name [Member]
Assets Acquired
Intangible assets						110
Waterfall International Inc. [Member] | Technology [Member]
Assets Acquired
Intangible assets						$ 2,800
RightAnswers, Inc. [Member]
Assets Acquired
Cash							$ 139
Accounts receivable							2,164
Other current assets							246
Property and equipment							408
Goodwill							15,680
Other assets							0
Total assets acquired							31,617
Liabilities Assumed
Accounts payable							(139)
Accrued expense and other							(2,108)
Deferred tax liabilities							0
Deferred revenue							(5,479)
Total liabilities assumed							(7,726)
Total consideration							23,891
RightAnswers, Inc. [Member] | Customer Relationships [Member]
Assets Acquired
Intangible assets							10,500
RightAnswers, Inc. [Member] | Trade Name [Member]
Assets Acquired
Intangible assets							180
RightAnswers, Inc. [Member] | Technology [Member]
Assets Acquired
Intangible assets							$ 2,300
Omtool, Ltd [Member]
Assets Acquired
Cash								$ 2,957
Accounts receivable								784
Other current assets								464
Property and equipment								58
Goodwill								14,081
Other assets								33
Total assets acquired								26,127
Liabilities Assumed
Accounts payable								(219)
Accrued expense and other								(915)
Deferred tax liabilities								0
Deferred revenue								(2,779)
Total liabilities assumed								(3,913)
Total consideration								22,214
Omtool, Ltd [Member] | Customer Relationships [Member]
Assets Acquired
Intangible assets								4,400
Omtool, Ltd [Member] | Trade Name [Member]
Assets Acquired
Intangible assets								170
Omtool, Ltd [Member] | Technology [Member]
Assets Acquired
Intangible assets								$ 3,180