Regulatory Capital and Reserve Requirements (Tables)

12 Months Ended

Dec. 31, 2011

REGULATORY CAPITAL AND RESERVE 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, 2011
Tier 1 capital (minimum-$2.5 billion (Consolidated))	$	6,582		$	6,596
Total capital (minimum-$5.1 billion (Consolidated))	9,015			8,849
Risk-weighted assets	63,244			63,029
Average assets (fourth quarter)	60,301			60,065
Tier 1 capital to risk-weighted assets (minimum-4.0%)	10.41		%	10.47		%
Total capital to risk-weighted assets (minimum-8.0%)	14.25			14.04
Tier 1 capital to average assets (minimum-3.0%)	10.92			10.98
December 31, 2010
Tier 1 capital (minimum-$2.4 billion (Consolidated))	$	6,027		$	6,073
Total capital (minimum-$4.8 billion (Consolidated))	8,651			8,455
Risk-weighted assets	59,506			59,278
Average assets (fourth quarter)	53,541			53,306
Tier 1 capital to risk-weighted assets (minimum-4.0%)	10.13		%	10.24		%
Total capital to risk-weighted assets (minimum-8.0%)	14.54			14.26
Tier 1 capital to average assets (minimum-3.0%)	11.26			11.39