Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Mortgage loan sale period	30 days
Advertising costs	$ 40	$ 38	$ 33
Interest Expense	478	528	543
Debt
Derivative [Line Items]
Interest Expense	$ 370	$ 409	$ 467
Minimum
Derivative [Line Items]
Loan commitment period	30 days
Maximum
Derivative [Line Items]
Loan commitment period	90 days