Fair Values of Assets and Liabilities (Summary of Balances of Assets and Liabilities Measured at Fair Value On A Recurring Basis) (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 2,998,898	$ 2,327,793	$ 2,430,749
Equity securities with readily determinable fair value	92,689	90,511	90,338
Loans held-for-investment	57,984		51,916
MSRs	199,146	147,571	124,316	$ 92,081
U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0	65,001
U.S. Government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	49,637	52,507	81,526
Municipal Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	155,489	165,594	148,300
Measured at fair value on a recurring basis:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account securities	852	1,061	951
Equity securities with readily determinable fair value	92,689	90,511	90,338
Mortgage loans held-for-sale	606,545	817,912	1,260,193
Loans held-for-investment	57,984	38,598	51,916
MSRs	199,146	147,571	124,316
Nonqualified deferred compensation assets	15,447	16,240	15,891
Derivative assets	153,534	165,008	253,509
Total	4,125,095	3,604,694	4,227,863
Derivative liabilities	122,107	123,000	200,758
Measured at fair value on a recurring basis: | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account securities	0	0	0
Equity securities with readily determinable fair value	84,623	82,445	82,272
Mortgage loans held-for-sale	0	0	0
Loans held-for-investment	0	0	0
MSRs	0	0	0
Nonqualified deferred compensation assets	0	0	0
Derivative assets	0	0	0
Total	84,623	82,445	147,273
Derivative liabilities	0	0	0
Measured at fair value on a recurring basis: | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account securities	852	1,061	951
Equity securities with readily determinable fair value	8,066	8,066	8,066
Mortgage loans held-for-sale	606,545	817,912	1,260,193
Loans held-for-investment	13,520	22,707	45,508
MSRs	0	0	0
Nonqualified deferred compensation assets	15,447	16,240	15,891
Derivative assets	150,087	154,448	227,875
Total	3,693,014	3,242,540	3,820,700
Derivative liabilities	122,107	123,000	200,758
Measured at fair value on a recurring basis: | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account securities	0	0	0
Equity securities with readily determinable fair value	0	0	0
Mortgage loans held-for-sale	0	0	0
Loans held-for-investment	44,464	15,891	6,408
MSRs	199,146	147,571	124,316
Nonqualified deferred compensation assets	0	0	0
Derivative assets	3,447	10,560	25,634
Total	347,458	279,709	259,890
Derivative liabilities	0	0	0
Measured at fair value on a recurring basis: | U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0	65,001
Measured at fair value on a recurring basis: | U.S. Treasury | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0	65,001
Measured at fair value on a recurring basis: | U.S. Treasury | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0	0
Measured at fair value on a recurring basis: | U.S. Treasury | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0	0
Measured at fair value on a recurring basis: | U.S. Government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	49,637	52,507	81,526
Measured at fair value on a recurring basis: | U.S. Government agencies | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0	0
Measured at fair value on a recurring basis: | U.S. Government agencies | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	49,637	52,507	79,742
Measured at fair value on a recurring basis: | U.S. Government agencies | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0	1,784
Measured at fair value on a recurring basis: | Municipal Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	155,489	165,594	148,300
Measured at fair value on a recurring basis: | Municipal Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0	0
Measured at fair value on a recurring basis: | Municipal Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	55,088	59,907	46,552
Measured at fair value on a recurring basis: | Municipal Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	100,401	105,687	101,748
Measured at fair value on a recurring basis: | Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	82,939	95,704	92,349
Measured at fair value on a recurring basis: | Corporate notes | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0	0
Measured at fair value on a recurring basis: | Corporate notes | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	82,939	95,704	92,349
Measured at fair value on a recurring basis: | Corporate notes | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0	0
Measured at fair value on a recurring basis: | Mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	2,710,833	2,013,988	2,043,573
Measured at fair value on a recurring basis: | Mortgage-backed | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0	0
Measured at fair value on a recurring basis: | Mortgage-backed | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	2,710,833	2,013,988	2,043,573
Measured at fair value on a recurring basis: | Mortgage-backed | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 0	$ 0	$ 0