Document and Entity Information
Oct. 21, 2020
Cover [Abstract]  
Document Type 8-K
Amendment Flag false
Document Period End Date Oct. 21, 2020
Entity Registrant Name Flagstar Bancorp, Inc.
Entity Central Index Key 0001033012
Entity Incorporation, State or Country Code MI
Entity File Number 1-16577
Entity Tax Identification Number 38-3150651
Entity Address, Address Line One 5151 Corporate Drive,
Entity Address, City or Town Troy,
Entity Address, State or Province MI
Entity Address, Postal Zip Code 48098
City Area Code 248
Local Phone Number 312-2000
Written Communications false
Soliciting Material false
Pre-commencement Tender Offer false
Pre-commencement Issuer Tender Offer false
Entity Emerging Growth Company false
Title of 12(b) Security Common stock
Trading Symbol FBC
Security Exchange Name NYSE