Description of Business and Summary of Significant Accounting Policies (Goodwill) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 01, 2018	Oct. 01, 2018	Sep. 30, 2018	Aug. 01, 2018	Jul. 01, 2018	Apr. 01, 2018	Feb. 01, 2018	Nov. 01, 2017	Oct. 01, 2017	Sep. 01, 2017	Jun. 01, 2017	Apr. 01, 2017	Nov. 01, 2016	Jul. 01, 2016
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill	$ 666,863,000	$ 441,404,000	$ 441,404,000
Goodwill, Impairment Loss	0	0	0
Goodwill [Roll Forward]
Goodwill, beginning balance	666,863,000	441,404,000
Additions for current year acquisitions	317,410,000	233,095,000
Purchase accounting adjustments for prior year acquisitions	(11,080,000)	(12,158,000)
Foreign currency translation adjustments	(26,508,000)	4,522,000
Goodwill, ending balance	946,685,000	666,863,000	$ 441,404,000
Oakstone, EbixHealth JV, IHAC(Hope), WDEV [Member], Itzcash, beBetter, Youirst, Wallstreet, Paul Merchants, and Via
Goodwill [Roll Forward]
Additions for current year acquisitions		220,937,000
Final Allocation | Oakstone, EbixHealth JV, IHAC(Hope), WDEV [Member], Itzcash, beBetter, Youirst, Wallstreet, Paul Merchants, and Via
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill	220,937,000	220,937,000
Goodwill, Period Increase (Decrease)	306,330,000
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 220,937,000
Goodwill, ending balance		$ 220,937,000
Final Allocation Adjustment | Oakstone; final purchase allocation adjustments
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill										$ 7,254,000
Final Allocation Adjustment | EbixHealth JV; final purchase allocation adjustments
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill																	$ (7,500,000)
Final Allocation Adjustment | Hope Health
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill																$ (289,000)
Final Allocation Adjustment | WDEV
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill																$ (5,317,000)
Final Allocation Adjustment | ItzCash
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill															$ (15,678,000)
Final Allocation Adjustment | Youfirst, WallStreet, and PML
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill													$ 4,736,000
Final Allocation Adjustment | Via
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill											$ (4,612,000)
Preliminary Allocation | CDL (Centrum)
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill									$ 159,647,000
Preliminary Allocation | Smartclass
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill									$ 16,568,000
Preliminary Allocation | Indus
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill								$ 21,501,000
Preliminary Allocation | Mercury
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill								16,215,000
Preliminary Allocation | Leisure
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill								$ 1,707,000
Preliminary Allocation | Miles
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill				$ 2,379,000			$ 19,075,000
Preliminary Allocation | Business Travels,Global Business Travels , and Subizz Travel
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill					$ 1,102,000
Preliminary Allocation | Pearl
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill				3,372,000
Preliminary Allocation | AHA Taxis
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill					281,000
Preliminary Allocation | Routier
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill					$ 455,000
Preliminary Allocation | ItzCash
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill															$ 119,766,000
Preliminary Allocation | beBetter
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill														$ 447,000
Preliminary Allocation | YouFirst
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill													$ 7,395,000
Preliminary Allocation | Wall Street
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill												$ 6,113,000
Preliminary Allocation | Paul Merchants
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill											38,589,000
Preliminary Allocation | Via
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill											$ 60,785,000
Preliminary Allocation | Weizmann
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill				$ 72,328,000
RCS
Goodwill [Line Items]
Business acquisition, purchase price allocation, goodwill						$ 80,800,000
Minimum | RCS, Broker, and Carrier [Member]
Goodwill [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate	5.00%
Minimum | Exchanges
Goodwill [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate	10.00%
Maximum | RCS, Broker, and Carrier [Member]
Goodwill [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate	9.00%
Maximum | Exchanges
Goodwill [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate	14.00%