XML 149 R131.htm IDEA: XBRL DOCUMENT v3.22.0.1
Regulatory Capital and Reserve Requirements Regulatory Capital and Reserve Requirements (Summary of Capital Position) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Summary of Capital Position [Line Items]    
Tier 1 capital $ 4,200 $ 4,000
Total capital 5,600 5,400
Minimum    
Summary of Capital Position [Line Items]    
CET 1 capital $ 3,100 $ 3,000
CET1 capital to risk-weighted assets 4.50% 4.50%
Tier1 capital to risk-weighted assets 6.00% 6.00%
Total capital to risk-weighted assets 8.00% 8.00%
Leverage ratio 4.00% 4.00%
Conservation buffer 2.50% 2.50%
Comerica Incorporated    
Summary of Capital Position [Line Items]    
CET 1 capital $ 7,064 $ 6,919
Tier 1 capital 7,458 7,313
Total capital 8,608 8,833
Risk-weighted assets 69,708 66,931
Average assets (fourth quarter) $ 96,417 $ 84,705
CET1 capital to risk-weighted assets 10.13% 10.34%
Tier1 capital to risk-weighted assets 10.70% 10.93%
Total capital to risk-weighted assets 12.35% 13.20%
Leverage ratio 7.74% 8.63%
Conservation buffer 4.35% 4.93%
Comerica Bank    
Summary of Capital Position [Line Items]    
CET 1 capital $ 7,634 $ 7,278
Tier 1 capital 7,634 7,278
Total capital 8,584 8,547
Risk-weighted assets 69,542 66,759
Average assets (fourth quarter) $ 96,216 $ 84,536
CET1 capital to risk-weighted assets 10.98% 10.90%
Tier1 capital to risk-weighted assets 10.98% 10.90%
Total capital to risk-weighted assets 12.34% 12.80%
Leverage ratio 7.93% 8.61%
Conservation buffer 4.34% 4.80%