Corporate Investments and Funds Held For Clients - Cash and Cash Equivalents and Investments (Details) - USD ($) $ in Thousands		Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Corporate Investments and Funds Held for Clients [Line Items]
Cash and cash equivalents, amortized cost		$ 360,594	$ 277,978
Funds held for clients cash and cash equivalents, amortized cost		3,600,570	1,534,894
Amortized cost		345,315
Total investments, amortized cost		4,306,479	2,124,551
Gross unrealized losses	[1]	(1,522)
Cash and cash equivalents, fair value		360,594	277,978	$ 215,093
Funds held for clients cash and cash equivalents, fair value		3,600,570	1,534,894
Fair value		343,793
Total investments, fair value		4,304,957	2,124,551
Available-for-sale Securities [Member] | Commercial Paper [Member]
Corporate Investments and Funds Held for Clients [Line Items]
Amortized cost	[2]	245,848	311,679
Gross unrealized losses	[1],[2]	(725)
Fair value	[2]	245,123	$ 311,679
Available-for-sale Securities [Member] | U.S. Treasury Securities [Member]
Corporate Investments and Funds Held for Clients [Line Items]
Amortized cost	[2]	74,467
Gross unrealized losses	[1],[2]	(797)
Fair value	[2]	73,670
Available-for-sale Securities [Member] | Certificates of Deposit [Member]
Corporate Investments and Funds Held for Clients [Line Items]
Amortized cost	[2]	25,000
Fair value	[2]	$ 25,000

[1] These securities have been in an unrealized loss position for a period of less than 12 months.

[2] All available-for-sale securities were included within funds held for clients.