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, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 3,259,845	$ 3,243,017	$ 2,998,898
Equity securities with readily determinable fair value	111,943	110,365	92,689
Loans held-for-investment	207,532		57,984
MSRs	224,470	230,225	199,146	$ 147,571
U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	4,948	14,948	0
U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	74,862	74,222	49,637
Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	160,386	168,655	155,489
Measured at fair value on a recurring basis:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account securities	102	1,127	852
Equity securities with readily determinable fair value	111,943	110,365	92,689
Mortgage loans held-for-sale	302,493	299,935	606,545
Loans held-for-investment	202,143	179,932	57,984
MSRs	224,470	230,225	199,146
Nonqualified deferred compensation assets	14,379	13,899	15,447
Derivative assets	274,004	296,848	153,534
Total	4,389,379	4,375,348	4,125,095
Derivative liabilities	274,432	338,078	122,107
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	103,877	102,299	84,623
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	108,825	117,247	84,623
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	102	1,127	852
Equity securities with readily determinable fair value	8,066	8,066	8,066
Mortgage loans held-for-sale	258,243	251,280	606,545
Loans held-for-investment	132,650	95,767	13,520
MSRs	0	0	0
Nonqualified deferred compensation assets	14,379	13,899	15,447
Derivative assets	268,648	295,137	150,087
Total	3,824,728	3,775,808	3,693,014
Derivative liabilities	274,432	338,078	122,107
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	44,250	48,655	0
Loans held-for-investment	69,493	84,165	44,464
MSRs	224,470	230,225	199,146
Nonqualified deferred compensation assets	0	0	0
Derivative assets	5,356	1,711	3,447
Total	455,826	482,293	347,458
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	4,948	14,948	0
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	4,948	14,948	0
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	74,862	74,222	49,637
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	74,862	74,222	49,637
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	0
Mortgage loans held-for-sale	44,250
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	160,386	168,655	155,489
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	48,129	51,118	55,088
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	112,257	117,537	100,401
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	83,675	85,705	82,939
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	83,675	85,705	82,939
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	2,935,974	2,899,487	2,710,833
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	2,935,974	2,899,487	2,710,833
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