Securities - Additional Information (Detail) $ in Thousands		3 Months Ended
		Mar. 31, 2020 USD ($) Investment	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) Investment
Schedule of Investments [Line Items]
Federal Home Loan Bank stock, at cost | $	[1]	$ 663,870		$ 647,562
Equity Securities, FV-NI, Unrealized Gain | $		$ 215,000	$ 1,600
Mortgage-Related Securities
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more				3
Capital trust notes
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more		5		5
Municipal bonds
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more		1		1
Mutual Fund
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more				1
US Government agencies securities
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more				7
Collateralized mortgage obligations
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more		5		3
Corporate bonds
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more		3		2
Asset-backed Securities
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more		7		3

[1] Carrying value and estimated fair value are at cost.