Borrowed Funds - Additional Information (Detail)		12 Months Ended
	Nov. 04, 2002 USD ($) age $ / shares shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Accrued interest		$ 23,400,000	$ 23,500,000
Short-term FHLB advances, average balance		$ 52,400,000		$ 3,300,000
Short-term FHLB advances, average balance, weighted average interest rate		1.90%		0.82%
Short-term FHLB advances, interest expense		$ 1,000,000.0		$ 27,000
Interest expense		$ 317,474,000	$ 279,329,000	222,454,000
Federal funds purchased				$ 47,900,000
Federal fund purchased Weighted average interest rate		1.70%	2.20%	2.20%
Federal funds purchased, average balance		$ 6.8	$ 620,000
Federal fund purchased, interest expenses		118,000	14,000	$ 418,000
Junior subordinated debentures		359,866,000	359,508,000
Short-term FHLB advances		1,000,000,000.0
Subordinated notes outstanding		295,100,000	294,700,000
Interest expense on subordinated notes		18,300,000	2,800,000
Repurchase Agreements
Debt Instrument [Line Items]
Accrued interest		1.7	287,000
Interest expense		17,700,000	6,800,000	16,400,000
Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Interest expense		259,000,000.0	248,000,000.0	186,000,000.0
Junior Subordinated Debt
Debt Instrument [Line Items]
Interest expense		22,400,000	21,700,000	19,600,000
New York Community Capital Trust V (BONUSESSM Units) | BONUSESSM units
Debt Instrument [Line Items]
Public offering of Bifurcated Option Note Unit Securities ("BONUSES units") | shares	5,500,000
Public offering of units, offering price per share | $ / shares	$ 50.00
Gross proceeds of BONUSES, debt	$ 275,000,000.0
Difference between the assigned value and the stated liquidation amount of the capital securities is treated as an original issue discount	92,400,000
Original issue discount amortized amount		65,800,000
New York Community Capital Trust V (BONUSESSM Units) | BONUSESSM units | Warrant
Debt Instrument [Line Items]
Gross proceeds of BONUSES	$ 92,400,000
New York Community Capital Trust V (BONUSESSM Units) | BONUSESSM units | Capital Units
Debt Instrument [Line Items]
Warrant to purchase, number of shares | age	2.4953
Warrant to purchase, total number of shares | shares	13,700,000
Warrant to purchase, exercise price per share | $ / shares	$ 20.04
Capital security, term (in years)	49 years
Capital security, coupon or distribution rate	6.00%
Capital security, per share liquidation amount | $ / shares	$ 50.00
Gross proceeds of BONUSES	$ 182,600,000
FHLB - NY
Debt Instrument [Line Items]
Unused line of credit		7,900,000,000	7,500,000,000
Overnight FHLB advances		100,000,000.0	0
Line of credit, average balance		$ 3,100,000	$ 5,200,000	$ 7,700,000
Line of credit, weighted average interest rate		2.10%	2.30%	0.98%
Interest expense		$ 66,000,000,000	$ 121,000	$ 75,000