Business Combinations - Pro Forma Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($)
Business Acquisition [Line Items]
Business Combination Bargain Purchase Gain Recognized Statement Of Income Or Comprehensive Income Extensible Enumeration Not Disclosed Flag	Interest Income (Expense), Operating
Flagstar Bancorp
Business Acquisition [Line Items]
Net interest income	$ 2,278
Non-interest income	650
Net income	804
Net income available to common stockholders	$ 771