Fair Value (Carrying and Estimated Fair Values of Financial Instruments) (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Financial Assets
Cash and interest bearing deposits	$ 3,477,800,000	$ 1,695,500,000	$ 1,190,100,000
Securities purchased under agreement to resell		950,000,000.0
Financial Liabilities
Credit balances of factoring clients	(1,023,700,000)	(1,176,200,000)	$ (1,651,300,000)
Level 2
Financial Assets
Securities purchased under agreement to resell	0
Carrying Value
Financial Assets
Cash and interest bearing deposits	3,698,500,000	2,685,600,000
Assets held for sale (excluding leases)	49,200,000	29,600,000
Loans (excluding leases)	36,278,900,000	28,744,500,000
Securities purchased under agreement to resell		950,000,000.0
Investment securities	273,900,000	217,800,000
Other assets subject to fair value disclosure	566,200,000	418,200,000
Financial Liabilities
Deposits	(42,182,000,000.0)	(35,156,200,000)
Borrowings	(8,121,400,000)	(6,549,600,000)
Credit balances of factoring clients	(1,023,700,000)	(1,176,200,000)
Other liabilities subject to fair value disclosure	(637,200,000)	(831,600,000)
Fair Value
Financial Assets
Cash and interest bearing deposits	3,698,500,000	2,685,600,000
Assets held for sale (excluding leases)	49,400,000	29,700,000
Loans (excluding leases)	33,262,800,000	28,798,800,000
Securities purchased under agreement to resell		950,000,000.0
Investment securities	273,900,000	217,800,000
Other assets subject to fair value disclosure	566,200,000	418,200,000
Financial Liabilities
Deposits	(42,334,200,000)	(35,263,800,000)
Borrowings	(7,982,500,000)	(6,897,200,000)
Credit balances of factoring clients	(1,023,700,000)	(1,176,200,000)
Other liabilities subject to fair value disclosure	(637,200,000)	(831,600,000)
Fair Value | Level 1
Financial Assets
Cash and interest bearing deposits	3,698,500,000	2,685,600,000
Assets held for sale (excluding leases)	0	0
Loans (excluding leases)	0	0
Securities purchased under agreement to resell		0
Investment securities	0	0
Other assets subject to fair value disclosure	0	0
Financial Liabilities
Deposits	0	0
Borrowings	0	0
Credit balances of factoring clients	0	0
Other liabilities subject to fair value disclosure	0	0
Fair Value | Level 2
Financial Assets
Cash and interest bearing deposits	0	0
Assets held for sale (excluding leases)	21,300,000	7,500,000
Loans (excluding leases)	855,900,000	1,114,500,000
Securities purchased under agreement to resell		950,000,000.0
Investment securities	0	0
Other assets subject to fair value disclosure	0	0
Financial Liabilities
Deposits	0	0
Borrowings	(7,430,600,000)	(6,532,000,000.0)
Credit balances of factoring clients	0	0
Other liabilities subject to fair value disclosure	0	0
Fair Value | Level 3
Financial Assets
Cash and interest bearing deposits	0	0
Assets held for sale (excluding leases)	28,100,000	22,200,000
Loans (excluding leases)	32,406,900,000	27,684,300,000
Securities purchased under agreement to resell		0
Investment securities	273,900,000	217,800,000
Other assets subject to fair value disclosure	566,200,000	418,200,000
Financial Liabilities
Deposits	(42,334,200,000)	(35,263,800,000)
Borrowings	(551,900,000)	(365,200,000)
Credit balances of factoring clients	(1,023,700,000)	(1,176,200,000)
Other liabilities subject to fair value disclosure	$ (637,200,000)	$ (831,600,000)