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Organization and Basis of Presentation - Additional Information (Detail)
 3 Months Ended 9 Months Ended
Dec. 31, 2018
Location
Sep. 30, 2018
Location
$ / shares
Dec. 31, 2017
$ / shares
Nov. 23, 1993
$ / shares
Organization and Basis Of Presentation [Line Items]        
Common stock, par | $ / shares   $ 0.01 $ 0.01 $ 0.01
Description of nine stock splits   ($0.93 per share on a split-adjusted basis, reflecting the impact of nine stock splits between 1994 and 2004).    
IPO        
Organization and Basis Of Presentation [Line Items]        
Shares issued, price per share | $ / shares       $ 25.00
Shares issued, price per share, split adjusted basis | $ / shares   $ 0.93    
New York Community Bank        
Organization and Basis Of Presentation [Line Items]        
Number of branches   223    
New York Commercial Bank        
Organization and Basis Of Presentation [Line Items]        
Number of branches   30    
Directly Operated Banks | New York Community Bank        
Organization and Basis Of Presentation [Line Items]        
Number of branches   2    
Seven Divisional Banks | New York Community Bank        
Organization and Basis Of Presentation [Line Items]        
Number of branches   221    
Atlantic Bank | New York Commercial Bank        
Organization and Basis Of Presentation [Line Items]        
Number of branches   18    
Scenario, Forecast | Merger New York Commercial Bank [Member] | New York Community Bank        
Organization and Basis Of Presentation [Line Items]        
Number of branches acquired in merger 30