Investment Securities - Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt securities available for sale:
Due in one year or less	$ 6,955
Due after one year through five years	2,895,828
Due after five years through ten years	30,344
Due after ten years	30,000
Total available for sale (amortized cost)	2,963,127
Mortgage-backed securities available for sale	2,820,570
Investment securities available for sale, amortized cost	5,783,697	$ 3,849,347
Debt securities held to maturity:
Due in one year or less	3,213
Due after ten years	2,487
Total available for held to maturity (amortized cost)	5,700
Mortgage-backed securities held to maturity	3,174,926
Amortized cost for held to maturity	3,180,626	2,734,674
Debt securities available for sale:
Due in one year or less	6,947
Due after one year through five years	2,846,337
Due after five years through ten years	30,018
Due after ten years	26,720
Total available for sale (fair value)	2,910,022
Mortgage-backed securities available for sale	2,795,177
Total	5,705,199	3,955,804
Debt securities held to maturity:
Due in one year or less	3,189
Due after ten years	2,487
Total available for held to maturity (fair value)	5,676
Mortgage-backed securities held to maturity	3,037,033
Total	$ 3,042,709	$ 2,771,290