Business Acquisitions (Narrative) (Details) - USD ($) $ in Thousands																1 Months Ended	12 Months Ended
	Dec. 01, 2018	Oct. 01, 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. 02, 2016	Jul. 02, 2016	Jul. 01, 2016	Sep. 01, 2015	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 01, 2016	Dec. 02, 2014
Business Acquisition [Line Items]
Business Acquisition, Earnout Accrual Adjustment																	$ 1,391	$ 164	$ 1,344
Derivative Liability																$ 24,976	24,976	37,096	8,510
Contingent liability for accrued earn-out acquisition consideration																11,209	11,209	33,096
Contingent liability for accrued earn-out acquisition consideration																13,767	13,767	4,000
Business acquisition, purchase price allocation, goodwill																946,685	946,685	666,863	441,404
Goodwill, Purchase Accounting Adjustments																	11,080	12,158
Goodwill																946,685	946,685	666,863	441,404
Payments to Acquire Interest in Joint Venture																	0	0	$ 696
Fair Value of Joint Venture, excluding Noncontrolling Interest											$ 120,000
Fair Value of Joint Venture, including Noncontrolling Interest											$ 150,000
Weizmann
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid	$ 63,100															21,100
Weizmann | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill	72,328
Goodwill	72,328
Pearl
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid	3,400
Pearl | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill	3,372
Goodwill	3,372
Lawson
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid	2,700
AHA Taxis
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid		$ 310
AHA Taxis | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill		281
Goodwill		281
Routier
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid		413
Routier | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill		455
Goodwill		455
Business Travels
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid		1,100
Miles
Business Acquisition [Line Items]
Derivative, Term of Contract			24 months
Business acquisition, cost of acquired entity, cash paid			$ 18,300
Miles | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill	2,379		19,075
Goodwill	$ 2,379		19,075
Via
Business Acquisition [Line Items]
Derivative, Term of Contract							12 months
Business acquisition, cost of acquired entity, cash paid							$ 78,800
Via | Final Allocation Adjustment
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill							(4,612)
Goodwill							(4,612)
Via | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill							60,785
Goodwill							60,785
WDEV
Business Acquisition [Line Items]
Derivative Liability																744	$ 744
Derivative, Term of Contract												38 months					38 months
Payments to Acquire Business, Held in Escrow												$ 2,900
Business acquisition, cost of acquired entity, cash paid												10,500
WDEV | Final Allocation Adjustment
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill																				$ (5,317)
Goodwill																				(5,317)
Hope
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid												$ 1,720
beBetter
Business Acquisition [Line Items]
Derivative, Term of Contract										24 months
Business acquisition, cost of acquired entity, cash paid										$ 1,000
beBetter | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill										447
Goodwill										447
ItzCash
Business Acquisition [Line Items]
Derivative Liability																$ 15,400	$ 15,400
Derivative, Term of Contract											36 months
Payments to Acquire Business, Held in Escrow											$ 4,000						$ 4,000
Escrow Derivative, Term of Contract											12 months
Business acquisition, cost of acquired entity, cash paid											$ 76,300
ItzCash | Final Allocation Adjustment
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill											(15,678)
Goodwill											(15,678)
ItzCash | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill											119,766
Goodwill											119,766
Oakstone | Final Allocation Adjustment
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill																					$ 948
Goodwill																					$ 948
PML
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid							37,400
Wall Street
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid								$ 7,400
Wall Street | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill								6,113
Goodwill								$ 6,113
YouFirst
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid									$ 10,200
YouFirst | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill									7,395
Goodwill									$ 7,395
Leisure
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid				$ 2,100
Leisure | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill				1,707
Goodwill				1,707
Mercury
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid				13,200
Mercury | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill				16,215
Goodwill				$ 16,215
Indus
Business Acquisition [Line Items]
Derivative, Term of Contract				24 months
Business acquisition, cost of acquired entity, cash paid				$ 22,900
Indus | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill				21,501
Goodwill				21,501
CDL (Centrum)
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid					$ 179,500
CDL (Centrum) | Preliminary Allocation
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill					159,647
Goodwill					159,647
Oakstone; final purchase allocation adjustments
Business Acquisition [Line Items]
Business acquisition, cost of acquired entity, cash paid						$ 7,250
Payments to Acquire Businesses, Net						6,550
Business Combination, Consideration Transferred, Liabilities Incurred						700
Oakstone; final purchase allocation adjustments | Final Allocation Adjustment
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, goodwill						7,254
Goodwill						$ 7,254
Maximum | Miles
Business Acquisition [Line Items]
Derivative Liability			$ 8,300
Maximum | WDEV
Business Acquisition [Line Items]
Derivative Liability																				$ 15,700
Maximum | beBetter
Business Acquisition [Line Items]
Derivative Liability										$ 2,000
Maximum | ItzCash
Business Acquisition [Line Items]
Derivative Liability											$ 44,000
Maximum | Indus
Business Acquisition [Line Items]
Derivative Liability				$ 5,000
Weizmann
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage	74.84%															25.16%	25.16%
AHA Taxis
Business Acquisition [Line Items]
Payments to Acquire Interest in Joint Venture		$ 310
Equity Method Investment, Ownership Percentage		70.00%
Routier
Business Acquisition [Line Items]
Payments to Acquire Interest in Joint Venture		$ 413
Equity Method Investment, Ownership Percentage		67.00%
Smartclass
Business Acquisition [Line Items]
Payments to Acquire Interest in Joint Venture					$ 8,600
Equity Method Investment, Ownership Percentage					60.00%
ItzCash
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage											80.00%
EbixHealth JV; final purchase allocation adjustments
Business Acquisition [Line Items]
Non-cash Payments To Acquire Interest In Joint Venture															$ 2,000
Equity Method Investment, Ownership Percentage Increase (Decrease)													11.00%	11.00%
Payments to Acquire Interest in Joint Venture													$ 2,000	$ 2,000	$ 6,000
Equity Method Investment, Ownership Percentage														51.00%	40.00%
Contingent Accrued Earn-out Acquisition Consideration
Business Acquisition [Line Items]
Derivative Liability																$ 24,980	$ 24,980	$ 37,100
Refund of Advance and withholding taxes | Via
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability							2,000
Potential claims made by tax authorities | Via
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability							$ 2,300