Borrowed Funds - Additional Information (Detail)			12 Months Ended
	Nov. 06, 2018 USD ($)	Nov. 04, 2002 USD ($) age $ / shares shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Accrued interest			$ 23,500,000	$ 19,300,000
Short-term FHLB advances, average balance				$ 3,300,000	$ 929,400,000,000
Short-term FHLB advances, average balance, weighted average interest rate				0.82%	0.60%
Short-term FHLB advances, interest expense				$ 27,000	$ 5,500,000
Interest expense			279,329,000	222,454,000	216,464,000
Federal funds purchased, average balance			$ 620,000,000,000	$ 47,900,000	$ 525,400,000
Federal fund purchased Weighted average interest rate			2.20%	0.87%	0.51%
Federal fund purchased, interest expenses			$ 14,000	$ 418,000,000,000	$ 2,700,000
Junior subordinated debentures			359,508,000	359,179,000
Repurchase Agreements
Debt Instrument [Line Items]
Accrued interest			287,000	760,000,000,000
Interest expense			6,800,000	16,400,000	23,300,000
Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Interest expense			248,000,000	186,000,000	172,000,000
Junior Subordinated Debt
Debt Instrument [Line Items]
Interest expense			21,700,000	19,600,000	18,500,000
Subordinated Debt
Debt Instrument [Line Items]
Capital security, coupon or distribution rate	5.90%
Principal amount of Subordinated Notes	$ 300,000,000
interest rate of subordinated note	5.90%
description of interest rate	LIBOR rate plus 278 basis points
maturity date of debt	Nov. 06, 2028
Issuance costs incurred relating to the offering			5,400,000
interest expense on subordinated notes			2,800,000
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
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			66,100,000
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
interest rate of subordinated note		6.00%
FHLB - NY
Debt Instrument [Line Items]
Unused line of credit			7,500,000,000	7,100,000,000
Line of credit, average balance			$ 5,200,000	$ 7,700,000	$ 426,500,000
Line of credit, weighted average interest rate			2.30%	0.98%	0.59%
Interest expense			$ 121,000,000,000	$ 75,000,000,000	$ 2,500,000