Share-Based Compensation Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement, Noncash Expense [Abstract]

Summary of Components of Share-Based Compensation Expense

The components of share-based compensation expense for all share-based compensation plans and related tax benefits are as follows:

(in millions)
Years Ended December 31	2019		2018		2017
Total share-based compensation expense	$	39	$	48	$	39
Related tax benefits recognized in net income	$	9	$	11	$	14

Schedule of Unrecognized Compensation Expense

The following table summarizes unrecognized compensation expense for all share-based plans.

(dollar amounts in millions)	December 31, 2019
Total unrecognized share-based compensation expense	$	33
Weighted-average expected recognition period (in years)	2.3

Estimated Weighted-Average Grant-Date Fair Value per Option and the Underlying Model Assumptions

The estimated weighted-average grant-date fair value per option and the underlying binomial option-pricing model assumptions are summarized in the following table:

Years Ended December 31	2019			2018			2017
Weighted-average grant-date fair value per option	$	22.27		$	30.32		$	19.61
Weighted-average assumptions:
Risk-free interest rates	2.74		%	2.63		%	2.47		%
Expected dividend yield	3.00			3.00			3.00
Expected volatility factors of the market price of    Comerica common stock	30			36			34
Expected option life (in years)	7.6			7.4			7.0

Summary of Stock Option Activity and Related Information

A summary of the Corporation’s stock option activity and related information for the year ended December 31, 2019 follows:

			Weighted-Average
	Number of Options (in thousands)		Exercise Price per Share		Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in millions)
Outstanding-January 1, 2019	2,943		$	44.70
Granted	283		80.14
Forfeited or expired	(35	)	65.91
Exercised	(511	)	37.32
Outstanding-December 31, 2019	2,680		49.58		5.3	$	66
Exercisable-December 31, 2019	1,816		$	41.79	4.2	$	56

Summary of Restricted Stock Activity and Related Information

A summary of the Corporation’s restricted stock activity and related information for the year ended December 31, 2019 follows:

	Number of Shares (in thousands)		Weighted-Average Grant-Date Fair  Value per Share
Outstanding-January 1, 2019	869		$	44.34
Forfeited	(27	)	49.81
Vested	(384	)	38.81
Outstanding-December 31, 2019	458		$	48.64

Summary of Restricted Stock Unit Activity and Related Information

A summary of the Corporation's restricted stock unit activity and related information for the year ended December 31, 2019 follows:

	Service-Based Units				Performance-Based Units
	Number of Units (in thousands)		Weighted-Average Grant-Date Fair  Value per Share		Number of Units (in thousands)		Weighted-Average Grant-Date Fair  Value per Share
Outstanding-January 1, 2019	367		$	68.14	662		$	56.64
Granted	237		78.81		329		66.80
Forfeited	(14	)	87.38		(28	)	81.06
Vested	(12	)	55.81		(420	)	32.53
Outstanding-December 31, 2019	578		72.34		543		80.22