Fair Value Measures - Quantitative Information about Recurring Level 3 Fair Value Financial Instruments (Details) $ in Millions	Dec. 31, 2023 USD ($) constant_default_rate_per_loan	Dec. 31, 2022 USD ($)
Assets:
Total debt securities available for sale | $	$ 9,145	$ 9,060
Private Label CMOs
Assets:
Total debt securities available for sale | $	180	191
Recurring
Assets:
Mortgage servicing rights | $	1,111	1,033
Recurring | Private Label CMOs
Assets:
Total debt securities available for sale | $	180	191
Recurring | Rate lock commitments (fallout-adjusted)
Liabilities:
Rate lock commitments (net) | $	$ 3	10
Weighted average life
Assets:
Mortgage servicing rights, measurement input	6.83
Significant Unobservable Inputs (Level 3) | Recurring
Assets:
Mortgage servicing rights | $	$ 1,111	1,033
Significant Unobservable Inputs (Level 3) | Recurring | Private Label CMOs
Assets:
Total debt securities available for sale | $	32	0
Significant Unobservable Inputs (Level 3) | Recurring | Rate lock commitments (fallout-adjusted)
Liabilities:
Rate lock commitments (net) | $	$ 3	$ 10
Significant Unobservable Inputs (Level 3) | Option adjusted spread | Minimum | Recurring
Assets:
Mortgage servicing rights, measurement input	0.050
Significant Unobservable Inputs (Level 3) | Option adjusted spread | Maximum | Recurring
Assets:
Mortgage servicing rights, measurement input	0.217
Significant Unobservable Inputs (Level 3) | Option adjusted spread | Weighted average | Recurring
Assets:
Mortgage servicing rights, measurement input	0.054
Significant Unobservable Inputs (Level 3) | Constant prepayment rate | Minimum | Recurring
Assets:
Mortgage servicing rights, measurement input	0
Significant Unobservable Inputs (Level 3) | Constant prepayment rate | Maximum | Recurring
Assets:
Mortgage servicing rights, measurement input	0.100
Significant Unobservable Inputs (Level 3) | Constant prepayment rate | Weighted average | Recurring
Assets:
Mortgage servicing rights, measurement input	0.079
Significant Unobservable Inputs (Level 3) | Weighted average cost to service per loan | Minimum | Recurring
Assets:
Mortgage servicing rights, measurement input	65.0
Significant Unobservable Inputs (Level 3) | Weighted average cost to service per loan | Maximum | Recurring
Assets:
Mortgage servicing rights, measurement input	90.0
Significant Unobservable Inputs (Level 3) | Weighted average cost to service per loan | Weighted average | Recurring
Assets:
Mortgage servicing rights, measurement input	69.0
Significant Unobservable Inputs (Level 3) | Origination pull-through rate | Recurring | Rate lock commitments (fallout-adjusted)
Liabilities:
Rate lock commitments (net), measurement input	0.6430
Significant Unobservable Inputs (Level 3) | Constant default rates | Minimum | Recurring | Private Label CMOs
Assets:
Private Label CMOs, measurement input	0.0010
Significant Unobservable Inputs (Level 3) | Constant default rates | Maximum | Recurring | Private Label CMOs
Assets:
Private Label CMOs, measurement input	0.0030
Significant Unobservable Inputs (Level 3) | Weighted average life | Minimum | Recurring | Private Label CMOs
Assets:
Private Label CMOs, measurement input	0.082
Significant Unobservable Inputs (Level 3) | Weighted average life | Maximum | Recurring | Private Label CMOs
Assets:
Private Label CMOs, measurement input	0.118
Significant Unobservable Inputs (Level 3) | Rate lock commitments (fallout-adjusted) | Recurring | Rate lock commitments (fallout-adjusted)
Liabilities:
Rate lock commitments (net) | $	$ 9