Regulatory Matters (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Tier One Leverage Capital
Tier 1 capital actual amount	$ 1,879	$ 1,720
Tier 1 capital (to adjusted tangible assets), actual ratio	8.09%	7.57%
Tier 1 capital, for capital adequacy purposes amount	$ 928	$ 909
Tier 1 capital (to adjusted tangible assets), for capital adequacy purposes ratio	4.00%	4.00%
Tier 1 capital capitalized under prompt corrective action provision amount	$ 1,161	$ 1,136
Tier 1 capital (to adjusted tangible assets), capitalized under prompt corrective action provision ratio	5.00%	5.00%
Common Equity Tier 1 Capital
Common equity Tier 1 capital (to RWA), actual amount	$ 1,639	$ 1,480
Common equity Tier 1 capital (to RWA), actual ratio	9.17%	9.32%
Common equity Tier 1 capital (to RWA), for capital adequacy purposes, amount	$ 804	$ 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	$ 1,161	$ 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	$ 1,879	$ 1,720
Tier 1 capital (to risk-weighted assets), actual ratio	10.52%	10.83%
Tier 1 capital, for capital adequacy purposes amount	$ 1,072	$ 953
Tier 1 capital (to risk-weighted assets), for capital adequacy purposes ratio	6.00%	6.00%
Tier 1 capital, capitalized under prompt corrective action provision amount	$ 1,429	$ 1,271
Tier 1 capital (to risk-weighted assets), capitalized under prompt corrective action provision ratio	8.00%	8.00%
Capital [Abstract]
Total capital, actual amount	$ 1,997	$ 1,830
Total capital (to risk-weighted assets), actual ratio	11.18%	11.52%
Total capital, for capital adequacy purposes amount	$ 1,429	$ 1,271
Total capital (to risk-weighted assets), for capital adequacy purposes ratio	8.00%	8.00%
Total capital, capitalized under prompt corrective action provisions amount	$ 1,786	$ 1,589
Total capital (to risk-weighted assets), capitalized under prompt corrective action provisions ratio	10.00%	10.00%
Bank
Tier One Leverage Capital
Tier 1 capital actual amount	$ 1,900	$ 1,752
Tier 1 capital (to adjusted tangible assets), actual ratio	8.19%	7.71%
Tier 1 capital, for capital adequacy purposes amount	$ 928	$ 909
Tier 1 capital (to adjusted tangible assets), for capital adequacy purposes ratio	4.00%	4.00%
Tier 1 capital capitalized under prompt corrective action provision amount	$ 1,160	$ 1,136
Tier 1 capital (to adjusted tangible assets), capitalized under prompt corrective action provision ratio	5.00%	5.00%
Common Equity Tier 1 Capital
Common equity Tier 1 capital (to RWA), actual amount	$ 1,900	$ 1,752
Common equity Tier 1 capital (to RWA), actual ratio	10.64%	11.04%
Common equity Tier 1 capital (to RWA), for capital adequacy purposes, amount	$ 804	$ 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	$ 1,161	$ 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	$ 1,900	$ 1,752
Tier 1 capital (to risk-weighted assets), actual ratio	10.64%	11.04%
Tier 1 capital, for capital adequacy purposes amount	$ 1,071	$ 952
Tier 1 capital (to risk-weighted assets), for capital adequacy purposes ratio	6.00%	6.00%
Tier 1 capital, capitalized under prompt corrective action provision amount	$ 1,429	$ 1,270
Tier 1 capital (to risk-weighted assets), capitalized under prompt corrective action provision ratio	8.00%	8.00%
Capital [Abstract]
Total capital, actual amount		$ 1,862
Total capital (to risk-weighted assets), actual ratio	11.30%	11.73%
Total capital, for capital adequacy purposes amount	$ 1,429	$ 1,270
Total capital (to risk-weighted assets), for capital adequacy purposes ratio	8.00%	8.00%
Total capital, capitalized under prompt corrective action provisions amount	$ 1,786	$ 1,587
Total capital (to risk-weighted assets), capitalized under prompt corrective action provisions ratio	10.00%	10.00%