Investment Securities - Summary of Securities Available for Sale in an Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	$ 3,978,371	$ 2,010,872
Less than 12 months, Unrealized Losses	266,941	25,813
12 months or longer, Fair Value	545,101	262,031
12 months or longer, Unrealized Losses	74,965	8,604
Total, Fair Value	4,523,472	2,272,903
Total, Unrealized Losses	341,906	34,417
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	383,535	75,106
Less than 12 months, Unrealized Losses	10,005	334
12 months or longer, Fair Value	170	213
12 months or longer, Unrealized Losses	3	3
Total, Fair Value	383,705	75,319
Total, Unrealized Losses	10,008	337
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	670,707	223,754
Less than 12 months, Unrealized Losses	76,647	2,872
12 months or longer, Fair Value	40,051	24,067
12 months or longer, Unrealized Losses	9,138	937
Total, Fair Value	710,758	247,821
Total, Unrealized Losses	85,785	3,809
Residential Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	1,051,557	680,320
Less than 12 months, Unrealized Losses	93,467	13,167
12 months or longer, Fair Value	216,233	71,392
12 months or longer, Unrealized Losses	36,647	2,655
Total, Fair Value	1,267,790	751,712
Total, Unrealized Losses	130,114	15,822
Residential Mortgage-Backed Securities, Non-agency [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	67,293	55,336
Less than 12 months, Unrealized Losses	3,187	726
12 months or longer, Fair Value	17,347	0
12 months or longer, Unrealized Losses	3,065	0
Total, Fair Value	84,640	55,336
Total, Unrealized Losses	6,252	726
Commercial Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	541,440	136,071
Less than 12 months, Unrealized Losses	27,157	2,912
12 months or longer, Fair Value	92,340	70,543
12 months or longer, Unrealized Losses	17,740	3,696
Total, Fair Value	633,780	206,614
Total, Unrealized Losses	44,897	6,608
Asset-backed Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	776,828	532,373
Less than 12 months, Unrealized Losses	30,045	2,620
12 months or longer, Fair Value	134,998	82,222
12 months or longer, Unrealized Losses	5,693	687
Total, Fair Value	911,826	614,595
Total, Unrealized Losses	35,738	3,307
Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	0	0
Less than 12 months, Unrealized Losses	0	0
12 months or longer, Fair Value	13,123	13,594
12 months or longer, Unrealized Losses	1,115	626
Total, Fair Value	13,123	13,594
Total, Unrealized Losses	1,115	626
Other corporate securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	487,011	307,912
Less than 12 months, Unrealized Losses	26,433	3,182
12 months or longer, Fair Value	30,839	0
12 months or longer, Unrealized Losses	1,564	0
Total, Fair Value	517,850	307,912
Total, Unrealized Losses	$ 27,997	$ 3,182