Debt (Narrative) (Details)						12 Months Ended
		Jan. 17, 2020 USD ($)	Mar. 30, 2015 USD ($)	Feb. 21, 2014 USD ($)	Jan. 22, 2014 USD ($)	Dec. 31, 2019 USD ($) facility		Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2016
Debt Instrument [Line Items]
Senior notes						$ 1,187,800,000		$ 544,400,000
Document Period End Date						Dec. 31, 2019
Maximum hedging reserve						$ 1,000,000.0
Percentage of collections on contributed loans						6.00%
Monthly servicing fee per financing						6.00%
Repayments of senior notes						$ 148,200,000		0	$ 0
Loss on extinguishment of debt						1,800,000		0	0
Debt covenants						1
Proceeds from issuance of senior notes						$ 800,000,000.0		0	$ 0
Revolving Secured Line Of Credit [Member]
Debt Instrument [Line Items]
Debt maturity date						Jun. 22, 2022
Line of credit facility						$ 340,000,000.0
Percentage of net book value of loans						80.00%
Warehouse Facilities [Member]
Debt Instrument [Line Items]
Percentage of net book value of loans						80.00%
Number of warehouse facilities | facility						6
Debt financing amount						$ 1,225,000,000.0
Warehouse Facility II [Member]
Debt Instrument [Line Items]
Debt maturity date	[1]					Jul. 12, 2022
Debt financing amount						$ 400,000,000.0	[2]	$ 400,000,000.0
Interest rate						0.00%		0.00%
Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Debt maturity date	[1]					Jul. 26, 2022
Debt financing amount						$ 300,000,000.0	[2]	$ 250,000,000.0
Interest rate						0.00%		0.00%
Warehouse Facility V [Member]
Debt Instrument [Line Items]
Debt maturity date	[3]					Aug. 17, 2021
Debt financing amount						$ 100,000,000.0	[2]	$ 100,000,000.0
Interest rate						0.00%		0.00%
Warehouse Facility VI [Member]
Debt Instrument [Line Items]
Debt maturity date	[1]					Sep. 30, 2022
Debt financing amount						$ 75,000,000.0
Interest rate						0.00%		0.00%
2017 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes stated interest rate										9.125%
Debt Instrument, Repurchase Date				Feb. 21, 2014
Repayments of senior notes				$ 350,000,000.0
Loss on extinguishment of debt				$ (21,800,000)
2021 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes						$ 151,800,000		$ 300,000,000.0
Debt Instrument, Issuance Date					Jan. 22, 2014
Debt maturity date					Feb. 15, 2021	Feb. 15, 2021	[4]
Debt financing amount					$ 300,000,000.0	$ 151,800,000
Senior notes stated interest rate					6.125%
Interest rate						6.125%		6.125%
2023 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes						$ 250,000,000.0		$ 250,000,000.0
Debt Instrument, Issuance Date			Mar. 30, 2015
Debt maturity date			Mar. 15, 2023			Mar. 15, 2023	[4]
Debt financing amount			$ 250,000,000.0			$ 250,000,000.0
Senior notes stated interest rate			7.375%
Redemption price, percentage of principal amount redeemed			99.266%
Proceeds from issuance of senior notes			$ 248,200,000
Interest rate			7.50%			7.375%		7.375%
2024 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes						$ 400,000,000.0		$ 0
Debt maturity date						Dec. 31, 2024
Debt financing amount						$ 400,000,000.0
Interest rate						5.125%		0.00%
2026 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes						$ 400,000,000.0		$ 0
Debt maturity date						Mar. 15, 2026
Debt financing amount						$ 400,000,000.0
Interest rate						6.625%		0.00%
Mortgage [Member]
Debt Instrument [Line Items]
Senior notes						$ 11,300,000		$ 11,900,000
Debt maturity date						Aug. 06, 2023
Debt financing amount						$ 12,000,000.0
Interest rate						3.21%		3.85%
London Interbank Offered Rate (LIBOR) [Member] | Revolving Secured Line Of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate						18750.00%
London Interbank Offered Rate (LIBOR) [Member] | Warehouse Facility II [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate						17500.00%
London Interbank Offered Rate (LIBOR) [Member] | Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate						20000.00%
London Interbank Offered Rate (LIBOR) [Member] | Warehouse Facility V [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate						19000.00%
London Interbank Offered Rate (LIBOR) [Member] | Warehouse Facility VI [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate						20000.00%
London Interbank Offered Rate (LIBOR) [Member] | Mortgage [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate						15000.00%
Prime Rate [Member] | Revolving Secured Line Of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate						8750.00%
Subsequent Event [Member] | 2021 Senior Notes [Member]
Debt Instrument [Line Items]
Repayments of senior notes		$ 151,800,000

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

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

[3] 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.

[4] On January 17, 2020, we used a portion of the net proceeds from the 2024 senior notes to redeem the remaining $151.8 million outstanding principal amount of the 2021 senior notes. We intend to use the remaining net proceeds from the 2024 senior notes, together with borrowings under our revolving credit facility and cash on hand to the extent available, to redeem in full the $250.0 million outstanding principal amount of the 2023 senior notes on or around March 15, 2020.