Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Statement of Cash Flows [Abstract]
Amortization of operating lease right-of-use assets	$ 4.1	$ 11.7
Amortization of operating lease liability	$ 4.1	$ 11.7

Amount of amortization expense attributable to right-of-use asset from operating lease right-of-use asset.

No definition available.

Name:	nycb_OperatingLeaseRightOfUseAssetAmortization
Namespace Prefix:	nycb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration