Fair Values of Assets and Liabilities (Summary of Changes in Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Loans held-for- investment
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 15,891	$ 10,280
Net income	(772)	(530)
Other comprehensive income (loss)	0	0
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	(1,667)	(3,918)
Net transfers into/(out of) Level 3	31,012	576
Ending balance	44,464	6,408
Mortgage servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	147,571	92,081
Net income	51,575	32,235
Other comprehensive income (loss)	0	0
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Net transfers into/(out of) Level 3	0	0
Ending balance	199,146	124,316
Derivative assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	10,560	48,091
Net income	(7,113)	(22,457)
Other comprehensive income (loss)	0	0
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Net transfers into/(out of) Level 3	0	0
Ending balance	3,447	25,634
Municipal Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	105,687	109,876
Net income	0	0
Other comprehensive income (loss)	(5,449)	(2,068)
Purchases	1,246	0
Issuances	0	0
Sales	0	0
Settlements	(1,083)	(6,060)
Net transfers into/(out of) Level 3	0	0
Ending balance	100,401	101,748
U.S. Government agencies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	1,966
Net income	0	0
Other comprehensive income (loss)	0	(24)
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	0	(158)
Net transfers into/(out of) Level 3	0	0
Ending balance	$ 0	$ 1,784