Regulatory Capital Requirements (Details)	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Regulatory Capital Requirements
Common Equity Tier 1 Capital (to risk weighted assets), ratio (as a percent)	10.30%	9.60%
Tier 1 Capital (to risk weighted assets), ratio (as a percent)	10.30%	9.60%
Total Capital (to risk weighted assets), ratio (as a percent)	12.60%	11.80%
Tier 1 Leverage ratio (as a percent)	8.30%	8.00%
Minimum | FDIC
Regulatory Capital Requirements
Common Equity Tier 1 Capital (to risk weighted assets), ratio (as a percent)	4.50%
Tier 1 Capital (to risk weighted assets), ratio (as a percent)	6.00%
Total Capital (to risk weighted assets), ratio (as a percent)	8.00%
Tier 1 Leverage ratio (as a percent)	4.00%
Basel III Capital Rules | FDIC
Regulatory Capital Requirements
Capital conservation buffer ratio	2.50%
Capital conservation buffer ratio annual increment during phase-in period	0.625%
Implementation period of capital conservation buffer requirement	4 years
Basel III Capital Rules | Minimum | FDIC
Regulatory Capital Requirements
Common Equity Tier 1 Capital (to risk weighted assets), ratio (as a percent)	7.00%
Tier 1 Capital (to risk weighted assets), ratio (as a percent)	8.50%
Total Capital (to risk weighted assets), ratio (as a percent)	10.50%