Fair Value - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Financial assets:
Loans receivable	$ 16,916,344	$ 18,335,197
Accrued loan interest receivable	780,691	788,552
Cash and cash equivalents	128,499	125,563	$ 212,989	$ 121,249
Restricted cash - due to customers	290,850	326,645	$ 247,673	$ 283,971
Financial liabilities:
Accrued interest payable	12,963	4,566
Bank deposits	588,474	344,315
Due to customers	409,476	366,002
Fair value
Financial assets:
Loans receivable	16,533,011	18,576,272
Accrued loan interest receivable	780,691	788,552
Cash and cash equivalents	128,499	125,563
Investments (at fair value)	1,331,482	1,001,655
Beneficial interest in loan securitizations	137,726	142,391
Restricted cash	754,693	741,981
Restricted cash - due to customers	290,850	326,645
Financial liabilities:
Bonds and notes payable	15,765,820	17,819,902
Accrued interest payable	12,963	4,566
Bank deposits	566,293	342,463
Due to customers	409,476	366,002
Fair value | Level 1
Financial assets:
Loans receivable	0	0
Accrued loan interest receivable	0	0
Cash and cash equivalents	128,499	125,563
Investments (at fair value)	7,398	63,254
Beneficial interest in loan securitizations	0	0
Restricted cash	754,693	741,981
Restricted cash - due to customers	290,850	326,645
Financial liabilities:
Bonds and notes payable	0	0
Accrued interest payable	0	0
Bank deposits	208,003	184,897
Due to customers	409,476	366,002
Fair value | Level 2
Financial assets:
Loans receivable	0	0
Accrued loan interest receivable	780,691	788,552
Cash and cash equivalents	0	0
Investments (at fair value)	1,294,437	929,569
Beneficial interest in loan securitizations	0	0
Restricted cash	0	0
Restricted cash - due to customers	0	0
Financial liabilities:
Bonds and notes payable	15,765,820	17,819,902
Accrued interest payable	12,963	4,566
Bank deposits	358,290	157,566
Due to customers	0	0
Fair value | Level 3
Financial assets:
Loans receivable	16,533,011	18,576,272
Accrued loan interest receivable	0	0
Cash and cash equivalents	0	0
Investments (at fair value)	0	0
Beneficial interest in loan securitizations	137,726	142,391
Restricted cash	0	0
Restricted cash - due to customers	0	0
Financial liabilities:
Bonds and notes payable	0	0
Accrued interest payable	0	0
Bank deposits	0	0
Due to customers	0	0
Carrying value
Financial assets:
Loans receivable	16,135,653	17,546,645
Accrued loan interest receivable	780,691	788,552
Cash and cash equivalents	128,499	125,563
Investments (at fair value)	1,331,482	1,001,655
Beneficial interest in loan securitizations	127,805	120,142
Restricted cash	754,693	741,981
Restricted cash - due to customers	290,850	326,645
Financial liabilities:
Bonds and notes payable	16,115,269	17,631,089
Accrued interest payable	12,963	4,566
Bank deposits	588,474	344,315
Due to customers	$ 409,476	$ 366,002