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Securities - Schedule of Fair Value and Amortized Cost of Available-for-sale and Held-to-maturity Securities (Detail) - USD ($)
$ in Thousands
Dec. 31, 2021
Dec. 31, 2020
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost $ 3,019,695 $ 1,916,658
Available-for-sale, Gross Unrealized Gains 30,542 63,237
Available-for-sale, Gross Unrealized Losses (36,775) (1,759)
Available-for-sale, Estimated Fair Value 3,013,462 1,978,136
Held-to-maturity, Amortized Cost 1,004,823 731,212
Held-to-maturity, Gross Unrealized Gains 27,153 37,030
Held-to-maturity, Gross Unrealized Losses (3,524) (59)
Held-to-maturity securities, Fair value 1,028,452 768,183
Total securities, Amortized Cost 4,024,518 2,647,870
Total securities, Gross Unrealized Gains 57,695 100,267
Total securities, Gross Unrealized Losses (40,299) (1,818)
Total securities, Estimated Fair Value 4,041,914 2,746,319
US Treasury Securities [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost   39,975
Available-for-sale, Gross Unrealized Gains   7
Available-for-sale, Estimated Fair Value   39,982
U.S. Government Sponsored Entities and Agencies [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 236,096 204,109
Available-for-sale, Gross Unrealized Gains 3,922 7,715
Available-for-sale, Gross Unrealized Losses (3,040) (142)
Available-for-sale, Estimated Fair Value 236,978 211,682
Held-to-maturity, Amortized Cost 5,944 7,779
Held-to-maturity, Gross Unrealized Gains 72 265
Held-to-maturity, Gross Unrealized Losses (8)  
Held-to-maturity securities, Fair value 6,008 8,044
Residential Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 2,301,170 1,230,106
Available-for-sale, Gross Unrealized Gains 16,489 35,979
Available-for-sale, Gross Unrealized Losses (32,446) (1,348)
Available-for-sale, Estimated Fair Value 2,285,213 1,264,737
Held-to-maturity, Amortized Cost 58,147 89,151
Held-to-maturity, Gross Unrealized Gains 1,409 3,251
Held-to-maturity, Gross Unrealized Losses (16)  
Held-to-maturity securities, Fair value 59,540 92,402
Commercial Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 364,486 308,903
Available-for-sale, Gross Unrealized Gains 4,252 11,464
Available-for-sale, Gross Unrealized Losses (1,245) (269)
Available-for-sale, Estimated Fair Value 367,493 320,098
Obligations of State and Political Subdivisions [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 101,003 108,602
Available-for-sale, Gross Unrealized Gains 5,372 7,160
Available-for-sale, Gross Unrealized Losses (35)  
Available-for-sale, Estimated Fair Value 106,340 115,762
Held-to-maturity, Amortized Cost 907,649 601,128
Held-to-maturity, Gross Unrealized Gains 23,854 30,173
Held-to-maturity, Gross Unrealized Losses (3,500) (59)
Held-to-maturity securities, Fair value 928,003 631,242
Corporate Debt Securities [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 16,940 24,963
Available-for-sale, Gross Unrealized Gains 507 912
Available-for-sale, Gross Unrealized Losses (9)  
Available-for-sale, Estimated Fair Value 17,438 25,875
Held-to-maturity, Amortized Cost 33,083 33,154
Held-to-maturity, Gross Unrealized Gains 1,818 3,341
Held-to-maturity securities, Fair value $ 34,901 $ 36,495