Debt (Schedule of General Information of Financing Transaction) - USD ($) $ in Millions				9 Months Ended
		Mar. 07, 2019	Aug. 06, 2018	Sep. 30, 2020		Dec. 31, 2019	Dec. 18, 2019
Debt Instrument [Line Items]
Senior notes				$ 790.1		$ 1,187.8
Revolving Secured Line of Credit [Member]
Debt Instrument [Line Items]
Line of credit maturity date				Jun. 22, 2022
Financing Amount				$ 340.0
Revolving Secured Line of Credit [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate				187.50%
Revolving Secured Line of Credit [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate				87.50%
Warehouse Facility II [Member]
Debt Instrument [Line Items]
Interest rate				1.91%		0.00%
Debt maturity date	[1],[2]			Jul. 12, 2022
Debt facility financing amount	[1],[3]			$ 400.0
Warehouse Facility II [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[1],[3]			175.00%
Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Interest rate				0.00%		0.00%
Debt maturity date	[1],[2]			Jul. 26, 2022
Debt facility financing amount				$ 300.0	[1],[3]	$ 300.0
Warehouse Facility IV [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[1],[3]			200.00%
Warehouse Facility V [Member]
Debt Instrument [Line Items]
Interest rate				0.00%		0.00%
Debt maturity date	[1],[4]			Aug. 17, 2021
Debt facility financing amount	[1],[3]			$ 100.0
Warehouse Facility V [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[1],[3]			190.00%
Warehouse Facility VI [Member]
Debt Instrument [Line Items]
Interest rate				2.16%		0.00%
Debt maturity date	[1],[2]			Sep. 30, 2022
Debt facility financing amount	[1]			$ 75.0
Warehouse Facility VI [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[1]			200.00%
Warehouse Facility VII [Member]
Debt Instrument [Line Items]
Interest rate				2.39%		0.00%
Debt maturity date	[1],[5]			Dec. 16, 2021
Debt facility financing amount	[1],[3]			$ 150.0
Warehouse Facility VII [Member] | Commercial Paper Offered Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[1],[3]			200.00%
Warehouse Facility VIII [Member]
Debt Instrument [Line Items]
Interest rate				0.00%		0.00%
Debt maturity date	[1],[2]			Jul. 26, 2022
Debt facility financing amount	[1],[3]			$ 200.0
Warehouse Facility VIII [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[1]			190.00%
Term ABS 2017-2 [Member]
Debt Instrument [Line Items]
Interest rate				3.24%		2.83%
Debt maturity date	[1],[2]			Jun. 17, 2019
Debt facility financing amount	[1]			$ 450.0
Term ABS 2017-3 [Member]
Debt Instrument [Line Items]
Interest rate				3.31%		2.91%
Debt maturity date	[1],[2]			Oct. 15, 2019
Debt facility financing amount	[1]			$ 350.0
Term ABS 2018-1 [Member]
Debt Instrument [Line Items]
Interest rate				3.43%		3.24%
Debt maturity date	[1],[2]			Feb. 17, 2020
Debt facility financing amount	[1]			$ 500.0
Term ABS 2018-2 [Member]
Debt Instrument [Line Items]
Interest rate				3.76%		3.68%
Debt maturity date	[1],[2]			May 15, 2020
Debt facility financing amount	[1]			$ 450.0
Term ABS 2018-3 [Member]
Debt Instrument [Line Items]
Interest rate				3.73%		3.72%
Debt maturity date	[1],[2]			Aug. 17, 2020
Debt facility financing amount	[1]			$ 398.3
Term ABS 2019-1 [Member]
Debt Instrument [Line Items]
Interest rate				3.53%		3.53%
Debt maturity date	[1],[2]			Feb. 15, 2021
Debt facility financing amount	[1]			$ 402.5
Term ABS 2019-2 [Member]
Debt Instrument [Line Items]
Interest rate				3.13%		3.13%
Debt maturity date	[1],[6]			Aug. 15, 2022
Debt facility financing amount	[1]			$ 500.0
Term ABS 2019-3 [Member]
Debt Instrument [Line Items]
Interest rate				2.56%		2.56%
Debt maturity date	[1],[2]			Nov. 15, 2021
Debt facility financing amount	[1]			$ 351.7
Term ABS 2020-1 [Member]
Debt Instrument [Line Items]
Interest rate				2.18%
Debt maturity date	[1],[2]			Feb. 15, 2022
Debt facility financing amount	[1]			$ 500.0
Term ABS 2020-2 [Member]
Debt Instrument [Line Items]
Interest rate				1.65%
Debt maturity date				Jul. 15, 2022
Debt facility financing amount				$ 481.8
2024 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes				$ 400.0		$ 400.0	$ 400.0
Interest rate				5.125%		5.125%	5.125%
Debt maturity date				Dec. 31, 2024
Debt facility financing amount				$ 400.0
2026 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes				$ 400.0		$ 400.0
Interest rate				6.625%		6.625%
Debt maturity date		Mar. 15, 2026		Mar. 15, 2026
Debt facility financing amount		$ 400.0		$ 400.0
Mortgages [Member]
Debt Instrument [Line Items]
Interest rate				1.66%		3.21%
Debt maturity date			Aug. 06, 2023	Aug. 06, 2023	[1]
Debt facility financing amount			$ 12.0	$ 12.0	[1]
Mortgages [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[1],[3]			150.00%

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

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

[3] Interest rate cap agreements are in place to limit the exposure to increasing interest rates

[4] Represents the revolving maturity date. The outstanding balance will amortize after the revolving maturity date and any amounts remaining on August 17, 2023 will be due on that date.

[5] Represents the revolving maturity date. The outstanding balance will amortize after the revolving maturity date and any amounts remaining on December 16, 2023 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.