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Organization, Basis of Presentation, and Impact of Recent Accounting Pronouncements - Additional Information (Details)
$ / shares in Units, $ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2021
USD ($)
Branch
$ / shares
Dec. 31, 2020
Branch
$ / shares
Dec. 31, 2019
$ / 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) ($0.93 per share on a split-adjusted basis, reflecting the impact of nine stock splits between 1994 and 2004).    
Cumulative effect on retained earnings, reduction in tax | $ $ 10.5      
Accounting Standards Update [Extensible List] Accounting Standards Update 2016-13 Accounting Standards Update 2016-13    
New York Community Bank        
Organization and Basis of Presentation [Line Items]        
Number of branches | Branch 237 237    
New York Community Bank | Corporate Segment        
Organization and Basis of Presentation [Line Items]        
Number of branches | Branch 19      
New York Community Bank | Corporate and Other        
Organization and Basis of Presentation [Line Items]        
Number of branches | Branch 218      
IPO        
Organization and Basis of Presentation [Line Items]        
Shares issued, price per share | $ / shares $ 25.00     $ 25.00
Shares issued, price per share, split adjusted basis | $ / shares $ 0.93 $ 0.93