Investment Securities (Summary of Debt Securities Held-to-Maturity) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	$ 6,198,339	$ 5,568,188
Interest Receivable	50,700	57,800
Collateralized Mortgage Obligations [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	42,405	91,622
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	2,901,593	2,419,751
Agency commercial mortgage-backed securities (agency CMBS) [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	2,378,475	2,101,227
Municipal Bonds [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	705,918	739,507
Commercial Mortgage Backed Securities [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	169,948	216,081
Moody's, Aaa Rating [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	377,374	425,457
Moody's, Aaa Rating [Member] | Collateralized Mortgage Obligations [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	0	0
Moody's, Aaa Rating [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	0	0
Moody's, Aaa Rating [Member] | Agency commercial mortgage-backed securities (agency CMBS) [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	0	0
Moody's, Aaa Rating [Member] | Municipal Bonds [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	207,426	209,376
Moody's, Aaa Rating [Member] | Commercial Mortgage Backed Securities [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	169,948	216,081
Moody's, Aa1 Rating [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	5,442,277	4,777,656
Moody's, Aa1 Rating [Member] | Collateralized Mortgage Obligations [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	42,405	91,622
Moody's, Aa1 Rating [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	2,901,593	2,419,751
Moody's, Aa1 Rating [Member] | Agency commercial mortgage-backed securities (agency CMBS) [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	2,378,475	2,101,227
Moody's, Aa1 Rating [Member] | Municipal Bonds [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	119,804	165,056
Moody's, Aa1 Rating [Member] | Commercial Mortgage Backed Securities [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	0	0
Moody's, Aa2 Rating [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	227,106	201,081
Moody's, Aa2 Rating [Member] | Municipal Bonds [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	227,106	201,081
Moody's, Aa3 Rating [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	104,232	115,619
Moody's, Aa3 Rating [Member] | Municipal Bonds [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	104,232	115,619
Moody's, A1 Rating [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	35,878	33,264
Moody's, A1 Rating [Member] | Municipal Bonds [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	35,878	33,264
Moody's, A2 Rating [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	8,260	8,475
Moody's, A2 Rating [Member] | Municipal Bonds [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	8,260	8,475
Moody's, A3 Rating [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	0	2,066
Moody's, A3 Rating [Member] | Municipal Bonds [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	0	2,066
Moody's, Baa2 Rating [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	95	190
Moody's, Baa2 Rating [Member] | Municipal Bonds [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	95	190
Moody's, Not Rated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	3,117	4,380
Moody's, Not Rated [Member] | Municipal Bonds [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Held to maturity securities	$ 3,117	$ 4,380