Fair Value of Assets and Liabilities - Fair Value Reconciliation (Detail) - Loans Invested in by Company - Loans Held For Sale - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Loans
Outstanding Principal Balance, Beginning	$ 62,761	$ 186,988	$ 147,193	$ 132,600
Valuation Adjustment, Beginning	50	(6,927)	(4,823)	(10,698)
Fair Value, Beginning	62,811	180,061	142,370	121,902
Outstanding Principal Balance, Originations and purchases	2,298,086	2,339,869	7,297,510	5,320,264
Valuation Adjustment, Originations and purchases	0	0	0	(1,629)
Fair Value, Originations and purchases	2,298,086	2,339,869	7,297,510	5,318,635
Outstanding Principal Balance, Sales	(2,264,859)	(2,342,158)	(7,315,612)	(5,210,803)
Valuation Adjustment, Sales	(188)	(85)	(18,979)	10,568
Fair Value, Sales	(2,265,047)	(2,342,243)	(7,334,591)	(5,200,235)
Outstanding Principal Balance, Principal payments and retirements	(4,592)	(27,211)	(24,990)	(78,946)
Valuation Adjustment, Principal payments and retirements	0	0	0	0
Fair Value, Principal payments and retirements	(4,592)	(27,211)	(24,990)	(78,946)
Outstanding Principal Balance, Charge-offs, net of recoveries	(17)	(1,138)	(834)	(6,765)
Valuation Adjustment, Charge-offs, net of recoveries	17	(209)	(628)	3,711
Fair Value, Charge-offs, net of recoveries	0	(1,347)	(1,462)	(3,054)
Outstanding Principal Balance, Change in fair value recorded in earnings	0	0	0	0
Valuation Adjustment, Change in fair value recorded in earnings	(1,200)	3,031	23,109	(6,142)
Fair Value, Change in fair value recorded in earnings	(1,200)	3,031	23,109	(6,142)
Outstanding Principal Balance, Transfers to/from loans held for investment			(11,888)
Valuation Adjustment, Transfers to/from loans held for investment			0
Fair Value, Transfers to/from loans held for investment			(11,888)
Outstanding Principal Balance, Ending	91,379	156,350	91,379	156,350
Valuation Adjustment, Ending	(1,321)	(4,190)	(1,321)	(4,190)
Fair Value, Ending	$ 90,058	$ 152,160	$ 90,058	$ 152,160