Securitizations and Variable Interest Entities - Summary of Select Information Related to VIEs (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Assets
Restricted cash	[1]	$ 77,577	$ 103,522
Securities available for sale at fair value		274,930	142,226
Loans held for sale at fair value	[1]	152,160	121,902
Retail and certificate loans held for investment at fair value	[1]	298,541	636,686
Other loans held for investment at fair value		2,603,256	0
Other assets	[1]	283,126	187,399
Total assets		4,750,760	1,863,293
Liabilities
Retail notes, certificates and secured borrowings at fair value	[1]	298,541	636,774
Payable on Structured Program borrowings	[1]	89,252	152,808
Other liabilities	[1]	265,840	244,551
Total liabilities		3,945,970	1,139,122
Consolidated VIEs
Assets
Restricted cash		14,827	15,983
Securities available for sale at fair value		0	0
Loans held for sale at fair value		55,172	98,190
Retail and certificate loans held for investment at fair value		15,388	52,620
Other loans held for investment at fair value		27,033	50,102
Other assets		649	1,270
Total assets		113,069	218,165
Liabilities
Retail notes, certificates and secured borrowings at fair value		15,388	52,620
Payable on Structured Program borrowings		89,252	152,808
Other liabilities		284	729
Total liabilities		104,924	206,157
Total net assets		8,145	12,008
Unconsolidated VIEs
Assets
Restricted cash		0	0
Securities available for sale at fair value		73,694	142,026
Loans held for sale at fair value		0	0
Retail and certificate loans held for investment at fair value		0	0
Other loans held for investment at fair value		0	0
Other assets		19,732	32,865
Total assets		93,426	174,891
Liabilities
Retail notes, certificates and secured borrowings at fair value		0	0
Payable on Structured Program borrowings		0	0
Other liabilities		0	0
Total liabilities		0	0
Total net assets		93,426	174,891
Total
Assets
Restricted cash		14,827	15,983
Securities available for sale at fair value		73,694	142,026
Loans held for sale at fair value		55,172	98,190
Retail and certificate loans held for investment at fair value		15,388	52,620
Other loans held for investment at fair value		27,033	50,102
Other assets		20,381	34,135
Total assets		206,495	393,056
Liabilities
Retail notes, certificates and secured borrowings at fair value		15,388	52,620
Payable on Structured Program borrowings		89,252	152,808
Other liabilities		284	729
Total liabilities		104,924	206,157
Total net assets		$ 101,571	$ 186,899

[1] Includes amounts in consolidated variable interest entities (VIEs) presented separately in the table below.