Regulatory Matters (Details) $ in Millions	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Tier One Leverage Capital
Tier 1 capital actual amount	$ 2,256	$ 1,720
Tier 1 capital (to adjusted tangible assets), actual ratio	0.080	0.076
Tier 1 capital, for capital adequacy purposes amount	$ 1,123	$ 909
Tier 1 capital (to adjusted tangible assets), for capital adequacy purposes ratio	0.040	0.040
Tier 1 capital capitalized under prompt corrective action provision amount	$ 1,403	$ 1,136
Tier 1 capital (to adjusted tangible assets), capitalized under prompt corrective action provision ratio	0.050	0.050
Common Equity Tier 1 Capital
Common equity Tier 1 capital (to RWA), actual amount	$ 2,016	$ 1,480
Common equity Tier 1 capital (to RWA), actual ratio	9.20%	9.30%
Common equity Tier 1 capital (to RWA), for capital adequacy purposes, amount	$ 985	$ 715
Common equity Tier 1 capital (to RWA), for capital adequacy purposes, ratio	4.50%	4.50%
Common equity Tier 1 capital (to RWA), well capitalized under prompt corrective action provisions, amount	$ 1,422	$ 1,033
Common equity Tier 1 capital (to RWA), well capitalized under prompt corrective action provisions, ratio	6.50%	6.50%
Tier One Risk Based Capital [Abstract]
Tier 1 capital, actual amount	$ 2,256	$ 1,720
Tier 1 capital (to risk-weighted assets), actual ratio	0.103	0.108
Tier 1 capital, for capital adequacy purposes amount	$ 1,313	$ 953
Tier 1 capital (to risk-weighted assets), for capital adequacy purposes ratio	0.060	0.060
Tier 1 capital, capitalized under prompt corrective action provision amount	$ 1,751	$ 1,271
Tier 1 capital (to risk-weighted assets), capitalized under prompt corrective action provision ratio	0.080	0.080
Capital [Abstract]
Total capital, actual amount	$ 2,471	$ 1,830
Total capital (to risk-weighted assets), actual ratio	0.113	0.115
Total capital, for capital adequacy purposes amount	$ 1,751	$ 1,271
Total capital (to risk-weighted assets), for capital adequacy purposes ratio	0.080	0.080
Total capital, capitalized under prompt corrective action provisions amount	$ 2,188	$ 1,589
Total capital (to risk-weighted assets), capitalized under prompt corrective action provisions ratio	0.100	0.100
Bank
Tier One Leverage Capital
Tier 1 capital actual amount	$ 2,212	$ 1,752
Tier 1 capital (to adjusted tangible assets), actual ratio	0.079	0.077
Tier 1 capital, for capital adequacy purposes amount	$ 1,122	$ 909
Tier 1 capital (to adjusted tangible assets), for capital adequacy purposes ratio	0.040	0.040
Tier 1 capital capitalized under prompt corrective action provision amount	$ 1,403	$ 1,136
Tier 1 capital (to adjusted tangible assets), capitalized under prompt corrective action provision ratio	0.050	0.050
Common Equity Tier 1 Capital
Common equity Tier 1 capital (to RWA), actual amount	$ 2,212	$ 1,752
Common equity Tier 1 capital (to RWA), actual ratio	10.10%	11.00%
Common equity Tier 1 capital (to RWA), for capital adequacy purposes, amount	$ 985	$ 714
Common equity Tier 1 capital (to RWA), for capital adequacy purposes, ratio	4.50%	4.50%
Common equity Tier 1 capital (to RWA), well capitalized under prompt corrective action provisions, amount	$ 1,422	$ 1,032
Common equity Tier 1 capital (to RWA), well capitalized under prompt corrective action provisions, ratio	6.50%	6.50%
Tier One Risk Based Capital [Abstract]
Tier 1 capital, actual amount	$ 2,212	$ 1,752
Tier 1 capital (to risk-weighted assets), actual ratio	0.101	0.110
Tier 1 capital, for capital adequacy purposes amount	$ 1,313	$ 952
Tier 1 capital (to risk-weighted assets), for capital adequacy purposes ratio	0.060	0.060
Tier 1 capital, capitalized under prompt corrective action provision amount	$ 1,751	$ 1,270
Tier 1 capital (to risk-weighted assets), capitalized under prompt corrective action provision ratio	0.080	0.080
Capital [Abstract]
Total capital, actual amount	$ 2,427	$ 1,862
Total capital (to risk-weighted assets), actual ratio	0.111	0.117
Total capital, for capital adequacy purposes amount	$ 1,751	$ 1,270
Total capital (to risk-weighted assets), for capital adequacy purposes ratio	0.080	0.080
Total capital, capitalized under prompt corrective action provisions amount	$ 2,188	$ 1,587
Total capital (to risk-weighted assets), capitalized under prompt corrective action provisions ratio	0.100	0.100