Debt - Collateralized Loan Obligation by Tranche (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Par Value Issued	$ 40,167	$ 29,167
Collateralized loan obligations	1,739,009	1,803,185
U.S. Bank National Association \| Secured Debt
Debt Instrument [Line Items]
Par Value Issued	1,825,201	2,186,563
Par Value Outstanding	1,753,451	1,822,345
Collateralized loan obligations	267,100	261,400
U.S. Bank National Association \| Secured Debt \| Tranche A Notes - 2017-FL2 Issuer
Debt Instrument [Line Items]
Par Value Issued		237,970
Par Value Outstanding		0
U.S. Bank National Association \| Secured Debt \| Tranche A-S Notes - 2017-FL2 Issuer
Debt Instrument [Line Items]
Par Value Issued		36,357
Par Value Outstanding		0
U.S. Bank National Association \| Secured Debt \| Tranche B Notes - 2017-FL2 Issuer
Debt Instrument [Line Items]
Par Value Issued		26,441
Par Value Outstanding		0
U.S. Bank National Association \| Secured Debt \| Tranche C Notes - 2017-FL2 Issuer
Debt Instrument [Line Items]
Par Value Issued		25,339
Par Value Outstanding		0
U.S. Bank National Association \| Secured Debt \| Tranche D Notes - 2017-FL2 Issuer
Debt Instrument [Line Items]
Par Value Issued		35,255
Par Value Outstanding		21,444
U.S. Bank National Association \| Secured Debt \| Tranche A Notes - 2018-FL3 Issuer
Debt Instrument [Line Items]
Par Value Issued	286,700	286,700
Par Value Outstanding	275,800	286,700
U.S. Bank National Association \| Secured Debt \| Tranche A-S Notes - 2018-FL3 Issuer
Debt Instrument [Line Items]
Par Value Issued	77,775	77,775
Par Value Outstanding	77,775	77,775
U.S. Bank National Association \| Secured Debt \| Tranche B Notes - 2018-FL3 Issuer
Debt Instrument [Line Items]
Par Value Issued	41,175	41,175
Par Value Outstanding	41,175	41,175
U.S. Bank National Association \| Secured Debt \| Tranche C Notes - 2018-FL3 Issuer
Debt Instrument [Line Items]
Par Value Issued	39,650	39,650
Par Value Outstanding	39,650	39,650
U.S. Bank National Association \| Secured Debt \| Tranche D Notes - 2018-FL3 Issuer
Debt Instrument [Line Items]
Par Value Issued	42,700	42,700
Par Value Outstanding	42,700	42,700
U.S. Bank National Association \| Secured Debt \| Tranche A Notes - 2018-FL4 Issuer
Debt Instrument [Line Items]
Par Value Issued	416,827	416,827
Par Value Outstanding	416,827	416,827
U.S. Bank National Association \| Secured Debt \| Tranche A-S Notes - 2018-FL4 Issuer
Debt Instrument [Line Items]
Par Value Issued	73,813	73,813
Par Value Outstanding	73,813	73,813
U.S. Bank National Association \| Secured Debt \| Tranche B Notes - 2018-FL4 Issuer
Debt Instrument [Line Items]
Par Value Issued	56,446	56,446
Par Value Outstanding	56,446	56,446
U.S. Bank National Association \| Secured Debt \| Tranche C Notes - 2018-FL4 Issuer
Debt Instrument [Line Items]
Par Value Issued	68,385	68,385
Par Value Outstanding	68,385	68,385
U.S. Bank National Association \| Secured Debt \| Tranche D Notes - 2018-FL4 Issuer
Debt Instrument [Line Items]
Par Value Issued	57,531	57,531
Par Value Outstanding	57,531	57,531
U.S. Bank National Association \| Secured Debt \| Tranche A Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Par Value Issued	407,025	407,025
Par Value Outstanding	407,025	407,025
U.S. Bank National Association \| Secured Debt \| Tranche A-S Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Par Value Issued	76,950	76,950
Par Value Outstanding	76,950	76,950
U.S. Bank National Association \| Secured Debt \| Tranche B Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Par Value Issued	50,000	50,000
Par Value Outstanding	50,000	50,000
U.S. Bank National Association \| Secured Debt \| Tranche C Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Par Value Issued	61,374	61,374
Par Value Outstanding	61,374	61,374
U.S. Bank National Association \| Secured Debt \| Tranche D Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Par Value Issued	48,600	48,600
Par Value Outstanding	5,000	24,300
U.S. Bank National Association \| Secured Debt \| Tranche E Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Par Value Issued	20,250	20,250
Par Value Outstanding	$ 3,000	$ 20,250
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche A Notes - 2017-FL2 Issuer
Debt Instrument [Line Items]
Interest Rate		0.82%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche A-S Notes - 2017-FL2 Issuer
Debt Instrument [Line Items]
Interest Rate		1.10%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche B Notes - 2017-FL2 Issuer
Debt Instrument [Line Items]
Interest Rate		1.40%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche C Notes - 2017-FL2 Issuer
Debt Instrument [Line Items]
Interest Rate		2.15%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche D Notes - 2017-FL2 Issuer
Debt Instrument [Line Items]
Interest Rate		3.45%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche A Notes - 2018-FL3 Issuer
Debt Instrument [Line Items]
Interest Rate	1.05%	1.05%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche A-S Notes - 2018-FL3 Issuer
Debt Instrument [Line Items]
Interest Rate	1.35%	1.35%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche B Notes - 2018-FL3 Issuer
Debt Instrument [Line Items]
Interest Rate	1.65%	1.65%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche C Notes - 2018-FL3 Issuer
Debt Instrument [Line Items]
Interest Rate	2.55%	2.55%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche D Notes - 2018-FL3 Issuer
Debt Instrument [Line Items]
Interest Rate	3.45%	3.45%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche A Notes - 2018-FL4 Issuer
Debt Instrument [Line Items]
Interest Rate	1.05%	1.05%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche A-S Notes - 2018-FL4 Issuer
Debt Instrument [Line Items]
Interest Rate	1.30%	1.30%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche B Notes - 2018-FL4 Issuer
Debt Instrument [Line Items]
Interest Rate	1.60%	1.60%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche C Notes - 2018-FL4 Issuer
Debt Instrument [Line Items]
Interest Rate	2.10%	2.10%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche D Notes - 2018-FL4 Issuer
Debt Instrument [Line Items]
Interest Rate	2.75%	2.75%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche A Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Interest Rate	1.15%	1.15%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche A-S Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Interest Rate	1.48%	1.48%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche B Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Interest Rate	1.40%	1.40%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche C Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Interest Rate	2.00%	2.00%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche D Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Interest Rate	2.40%	2.40%
1M LIBOR \| U.S. Bank National Association \| Secured Debt \| Tranche E Notes - 2019-FL5 Issuer
Debt Instrument [Line Items]
Interest Rate	2.85%	2.85%

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

+ References

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- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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