Regulatory Capital and Reserve Requirements Regulatory Capital and Reserve Requirements (Tables)

12 Months Ended

Dec. 31, 2018

Regulatory Capital Requirements [Abstract]

Summary of Capital Position

The following is a summary of the capital position of the Corporation and Comerica Bank, its principal banking subsidiary.

(dollar amounts in millions)	Comerica Incorporated (Consolidated)			Comerica Bank
December 31, 2018
CET1 capital (minimum $3.0 billion (Consolidated))	$	7,470		$	7,229
Tier 1 capital (minimum $4.0 billion (Consolidated))	7,470			7,229
Total capital (minimum $5.4 billion (Consolidated))	8,855			8,433
Risk-weighted assets	67,047			66,857
Average assets (fourth quarter)	71,070			70,905
CET1 capital to risk-weighted assets (minimum-4.5%)	11.14		%	10.81		%
Tier 1 capital to risk-weighted assets (minimum-6.0%)	11.14			10.81
Total capital to risk-weighted assets (minimum-8.0%)	13.21			12.61
Tier 1 capital to average assets (minimum-4.0%)	10.51			10.20
Capital conservation buffer	5.14			4.61
December 31, 2017
CET1 capital (minimum $3.0 billion (Consolidated))	$	7,773		$	7,121
Tier 1 capital (minimum $4.0 billion (Consolidated))	7,773			7,121
Total capital (minimum $5.3 billion (Consolidated))	9,211			8,378
Risk-weighted assets	66,575			66,447
Average assets (fourth quarter)	71,372			71,181
CET1 capital to risk-weighted assets (minimum-4.5%)	11.68		%	10.72		%
Tier 1 capital to risk-weighted assets (minimum-6.0%)	11.68			10.72
Total capital to risk-weighted assets (minimum-8.0%)	13.84			12.61
Tier 1 capital to average assets (minimum-4.0%)	10.89			10.00
Capital conservation buffer	5.68			4.61