Investment Securities - Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Debt securities available for sale:
Due in one year or less	$ 1,871,549
Due after one year through five years	6,142,735
Due after five years through ten years	50,702
Due after ten years	30,000
Total available for sale (amortized cost)	8,094,986
Mortgage-backed securities available for sale	3,298,930
Investment securities available for sale, amortized cost	11,393,916	$ 11,193,152
Debt securities held to maturity:
Due in one year or less	86,180
Due after one year through five years	1,120,699
Due after five years through ten years	1,143,823
Due after ten years	1,271,794
Total available for held to maturity (amortized cost)	3,622,496
Mortgage-backed securities held to maturity	12,579,075
Amortized cost for held to maturity	16,201,571	13,529,969
Debt securities available for sale:
Due in one year or less	1,824,693
Due after one year through five years	5,999,076
Due after five years through ten years	47,804
Due after ten years	25,450
Total available for sale (fair value)	7,897,023
Mortgage-backed securities available for sale	3,141,899
Total	11,038,922	10,748,961
Debt securities held to maturity:
Due in one year or less	85,572
Due after one year through five years	1,084,851
Due after five years through ten years	1,130,492
Due after ten years	1,213,966
Total available for held to maturity (fair value)	3,514,881
Mortgage-backed securities held to maturity	11,689,580
Total	$ 15,204,461	$ 12,375,420