Acquisitions - Narrative (Details) $ in Thousands, € in Millions, shares in Millions							3 Months Ended
	Jan. 24, 2020 USD ($) shares	Jul. 01, 2019 USD ($)	Jul. 01, 2019 EUR (€)	Mar. 05, 2019 USD ($)	Feb. 14, 2019 USD ($)	Jan. 24, 2019 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Business Acquisition [Line Items]
Purchase price of acquisition, net of cash acquired							$ 0	$ 568,426
Goodwill							$ 2,418,288		$ 2,441,201
eNett
Business Acquisition [Line Items]
Cash to be paid	$ 1,300,000
Shares to be issued (in shares) | shares	2.0
Go Fuel Card
Business Acquisition [Line Items]
Consideration transferred		$ 266,000	€ 235.0
Goodwill		$ 118,746
Weighted average life (in years)		8 years 10 months 24 days	8 years 10 months 24 days
Discovery Benefits
Business Acquisition [Line Items]
Consideration transferred				$ 526,100
Deferred cash consideration				50,000
Fair value of equity interests acquired				100,000
Purchase price of acquisition, net of cash acquired				300,191
Goodwill				272,399
Accounts receivable acquired				$ 10,722
Weighted average life (in years)				7 years
Pavestone Capital
Business Acquisition [Line Items]
Purchase price of acquisition, net of cash acquired					$ 28,000
Goodwill					9,500
Accounts receivable acquired					14,900
Noventis
Business Acquisition [Line Items]
Consideration transferred						$ 338,700
Goodwill						209,887
Accounts receivable acquired						$ 22,134
Weighted average life (in years)						7 years 7 months 6 days
Amount of accelerated vesting of options						$ 5,500
Customer relationships | Go Fuel Card
Business Acquisition [Line Items]
Customer relationships acquired		$ 33,963
Weighted average life (in years)		5 years	5 years
Customer relationships | Discovery Benefits
Business Acquisition [Line Items]
Customer relationships acquired				$ 213,600
Weighted average life (in years)				7 years 3 months 18 days
Customer relationships | Pavestone Capital
Business Acquisition [Line Items]
Customer relationships acquired					$ 3,900
Weighted average life (in years)				6 years 6 months
Customer relationships | Noventis
Business Acquisition [Line Items]
Customer relationships acquired						$ 100,900
Weighted average life (in years)						8 years 3 months 18 days
Discovery Benefits
Business Acquisition [Line Items]
Ownership percentage by noncontrolling interest				4.90%