Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands		Mar. 31, 2020		Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		$ 5,487,861	[1]	$ 5,885,887	[2]
Total equity securities		32,616		32,830
Total securities		5,487,861		5,885,887
Mutual Funds and Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	[3]	17,775		17,416
Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	[4]	355,383		373,254
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		5,455,245		5,853,057
Total equity securities		32,616		32,830
Total securities		5,487,861		5,885,887
Fair Value, Measurements, Recurring | Preferred stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total equity securities		14,841		15,414
Fair Value, Measurements, Recurring | Mutual Funds and Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total equity securities		17,775		17,416
Fair Value, Measurements, Recurring | Mortgage-Related Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		3,407,542		3,353,735
Fair Value, Measurements, Recurring | Mortgage-Related Securities | GSE certificates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		1,493,269		1,552,623
Fair Value, Measurements, Recurring | Mortgage-Related Securities | GSE CMOs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		1,914,273		1,801,112
Fair Value, Measurements, Recurring | Other Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		2,047,703		2,499,322
Fair Value, Measurements, Recurring | Other Securities | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		61,981		41,839
Fair Value, Measurements, Recurring | Other Securities | GSE debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		725,232		1,094,240
Fair Value, Measurements, Recurring | Other Securities | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		792,834		867,182
Fair Value, Measurements, Recurring | Other Securities | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		26,746		26,892
Fair Value, Measurements, Recurring | Other Securities | Capital trust notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		85,527		95,915
Fair Value, Measurements, Recurring | Other Securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		355,383		373,254
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		61,981		41,839
Total equity securities		14,841		15,414
Total securities		76,822		57,253
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Preferred stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total equity securities		14,841		15,414
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		61,981		41,839
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Securities | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		61,981		41,839
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		5,393,264		5,811,218
Total equity securities		17,775		17,416
Total securities		5,411,039		5,828,634
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Mutual Funds and Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total equity securities		17,775		17,416
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-Related Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		3,407,542		3,353,735
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-Related Securities | GSE certificates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		1,493,269		1,552,623
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-Related Securities | GSE CMOs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		1,914,273		1,801,112
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		1,985,722		2,457,483
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other Securities | GSE debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		725,232		1,094,240
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other Securities | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		792,834		867,182
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other Securities | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		26,746		26,892
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other Securities | Capital trust notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		85,527		95,915
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other Securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale		$ 355,383		$ 373,254

[1] Excludes accrued interest receivable of $20.6 million included in other assets in the Consolidated Statements of Condition.

[2] Excludes accrued interest receivable of $24.4 million included in other assets in the Consolidated Statements of Condition.

[3] Primarily consists of mutual funds that are CRA-qualified investments.

[4] The underlying assets of the asset-backed securities are substantially guaranteed by the U.S. Government.