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Securities - Additional Information (Detail) $ in Thousands		12 Months Ended
		Dec. 31, 2019 USD ($) Investment	Dec. 31, 2018 USD ($) Investment	Dec. 31, 2017 USD ($)
Schedule of Investments [Line Items]
Federal Home Loan Bank stock, at cost	[1]	$ 647,562	$ 644,590
Amortized cost from sales of held to maturity securities				$ 521,000
Proceeds from sales of held to maturity securities				547,925
Gross realized gains from sales of held to maturity securities				26,900
Securities transferred from held to maturity to available for sale				3,040,305
Unrealized gain on securities transferred from held to maturity to available for sale				$ 82,800
Investment securities designated as having a continuous loss position for twelve months or more, unrealized losses		$ 14,800	$ 22,500
Investment securities designated as having a continuous loss position for twelve months or more, percentage below collective amortized cost		2.30%	2.90%
Investment securities designated as having a continuous loss position for twelve months or more, amortized cost		$ 642,300	$ 782,400
Equity Securities, FV-NI, Unrealized Gain		$ 2,300	$ 2,000
Mortgage-Related Securities
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more | Investment		3	9
Capital trust notes
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more | Investment		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 | Investment		1	3
Mutual Fund
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more | Investment		1	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 | Investment		7	9
Collateralized mortgage obligations
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more | Investment		3	7
Corporate bonds
Schedule of Investments [Line Items]
Number of investment securities designated as having a continuous loss position for twelve months or more | Investment		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 | Investment		3
[1] Carrying value and estimated fair value are at cost.

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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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