Debt (Narrative) (Details) - USD ($) $ in Millions			3 Months Ended			6 Months Ended
		Mar. 07, 2019	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2023		Mar. 31, 2023	Dec. 31, 2022	Dec. 18, 2019	Aug. 06, 2018
Debt Instrument [Line Items]
Maximum hedging reserve						$ 1.0
Unamortized Debt Issuance Costs						$ (24.6)			$ (22.4)
Percentage of collections on newer contributed loans						4.00%
Percentage of collections on contributed loans						6.00%
Monthly servicing fee per financing						6.00%
Monthly servicing fee per newer financings						4.00%
Mortgage note	[1]					$ 8.6			8.9
Repayment of senior notes					$ 148.2
Senior notes						794.9			794.5
Loss on extinguishment of debt			$ 7.4		$ 1.8
Carrying Amount						4,746.6			4,590.7
Senior Notes [Member]
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs						(5.1)			(5.5)
Carrying Amount						794.9			794.5
Mortgages [Member]
Debt Instrument [Line Items]
Debt facility financing amount						9.0	[2]				$ 9.0
Unamortized Debt Issuance Costs						0.0			0.0
Mortgage note						$ 8.6			$ 8.9
Debt maturity date	[2]					Aug. 06, 2028
Senior notes yield to maturity						6.60%			5.46%
Carrying Amount						$ 8.6			$ 8.9
Revolving Secured Line of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility						$ 390.0
Percentage of net book value of loans						80.00%
Unamortized Debt Issuance Costs	[3]					$ 0.0			0.0
Carrying Amount	[3]					$ 168.9			$ 30.9
Warehouse Facilities [Member]
Debt Instrument [Line Items]
Percentage of net book value of loans						80.00%
Number of warehouse facilities						5
Debt facility financing amount						$ 1,175.0
Warehouse Facility II [Member]
Debt Instrument [Line Items]
Debt facility financing amount	[2]					$ 400.0
Debt maturity date	[2],[4]					Apr. 30, 2026
Senior notes yield to maturity						0.00%			0.00%
Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Debt facility financing amount	[2]					$ 300.0
Debt maturity date	[2],[4]					May 20, 2025
Senior notes yield to maturity						0.00%			0.00%
Warehouse Facility V [Member]
Debt Instrument [Line Items]
Debt facility financing amount	[2]					$ 200.0
Debt maturity date	[2],[5]					Dec. 29, 2025
Senior notes yield to maturity						0.00%			0.00%
Warehouse Facility VI [Member]
Debt Instrument [Line Items]
Debt facility financing amount	[2]					$ 75.0
Debt maturity date	[2],[4]					Sep. 30, 2024
Senior notes yield to maturity						0.00%			0.00%
Term ABS 2019-2 [Member]
Debt Instrument [Line Items]
Debt facility financing amount	[2]					$ 500.0
Debt financing close date						Aug. 28, 2019
Debt maturity date	[2],[6]					Aug. 15, 2025
Senior notes yield to maturity						5.15%			5.15%
Net Book Value Of Loans Pledged As Collateral						$ 625.1
Term ABS 2019-3 [Member]
Debt Instrument [Line Items]
Senior notes yield to maturity						0.00%			3.00%
Term ABS 2020-1 [Member]
Debt Instrument [Line Items]
Senior notes yield to maturity						0.00%			2.51%
Term ABS 2020-2 [Member]
Debt Instrument [Line Items]
Debt facility financing amount	[2]					$ 481.8
Debt financing close date						Jul. 23, 2020
Debt maturity date	[2],[4]					Jul. 15, 2022
Senior notes yield to maturity						2.29%			1.81%
Net Book Value Of Loans Pledged As Collateral						$ 602.3
2021 Senior Notes [Member]
Debt Instrument [Line Items]
Debt facility financing amount										$ 300.0
Repayment of senior notes				$ 151.8
Senior notes yield to maturity										6.125%
2024 Senior Notes [Member]
Debt Instrument [Line Items]
Debt facility financing amount						$ 400.0
Debt maturity date						Dec. 31, 2024
Senior notes						$ 400.0			$ 400.0	$ 400.0
Senior notes yield to maturity						5.125%			5.125%	5.125%
2026 Senior Notes [Member]
Debt Instrument [Line Items]
Debt facility financing amount		$ 400.0				$ 400.0
Close date, secured financings		Mar. 07, 2019
Senior notes stated interest rate		6.625%
Debt maturity date		Mar. 15, 2026				Mar. 15, 2026
Senior notes						$ 400.0			$ 400.0
Senior notes yield to maturity						6.625%			6.625%
2023 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes								$ 250.0
Senior notes yield to maturity										7.375%
Term ABS 2021-2 [Member]
Debt Instrument [Line Items]
Debt facility financing amount	[2]					$ 500.0
Debt financing close date						Feb. 18, 2021
Debt maturity date	[2],[4]					Feb. 15, 2023
Senior notes yield to maturity						1.18%			1.12%
Net Book Value Of Loans Pledged As Collateral						$ 625.1
Prime Rate [Member] | Revolving Secured Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate						87.50%

[1] Measured at amortized cost with fair value disclosed.

[2] Financing made available only to a specified subsidiary of the Company.

[3] Excludes deferred debt issuance costs of $4.9 million and $3.9 million as of June 30, 2023 and December 31, 2022, respectively, which are included in other assets.

[4] Represents the revolving maturity date. The outstanding balance will amortize after the revolving maturity date based on the cash flows of the pledged assets.

[5] Represents the revolving maturity date. The outstanding balance will amortize after the revolving maturity date and any amounts remaining on December 27, 2027 will be due on that date.

[6] Represents the revolving maturity date. The Company has the option to redeem and retire the indebtedness after the revolving maturity date. If we do not elect this option, the outstanding balance will amortize based on the cash flows of the pledged assets