Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2019

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Activity in Corporation's Active Stock Plans

A combined summary of activity in our active stock plans is presented in the table. Performance stock units outstanding are presented assuming attainment of the maximum payout rate as set forth by the performance criteria. As of September 30, 2019, there were 1,277,578 shares remaining available for grant for future stock-based compensation awards.

	Director Deferred Stock Units Outstanding				Non-Vested Stock Awards/Stock Units Outstanding				Performance Stock Units Outstanding			Stock Options Outstanding
	Number of Units		Weighted- Average Fair Value at Grant		Number of Shares/Units		Weighted- Average Fair Value at Grant		Number of Units	Weighted- Average Fair Value at Grant		Number of Shares		Weighted- Average Exercise Price
Balance, January 1, 2019	48,910		$	71.14	383,797		$	85.59	125,809	$	82.55	2,352,008		$	63.55
Authorized	—		—		—		—		—	—		—		—
Granted	7,592		102.70		1,957		91.96		—	—		—		—
Exercised/vested	(1,132	)	106.03		(17,800	)	65.11		—	—		(236,252	)	57.17
Forfeited/expired	—		—		(11,850	)	89.29		—	—		(11,000	)	65.11
Balance, September 30, 2019	55,370		$	74.76	356,104		$	86.53	125,809	$	82.55	2,104,756		$	64.26

Shares Issued in Connection with Stock Compensation Awards

Shares issued in connection with stock compensation awards along with other related information were as follows:

	Three Months Ended   September 30,				Nine Months Ended   September 30,
	2019		2018		2019		2018
New shares issued from available authorized shares	—		—		—		—
Issued from available treasury stock	71,284		19,232		225,184		447,831
Total	71,284		19,232		225,184		447,831
Proceeds from stock option exercises	$	5,665	$	1,119	$	13,506	$	26,567

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block]

Stock-based compensation expense and the related income tax benefit is presented in the following table.

	Three Months Ended   September 30,				Nine Months Ended   September 30,
	2019		2018		2019		2018
Stock options	$	330	$	960	$	1,091	$	3,064
Non-vested stock awards/stock units	1,536		1,357		5,727		4,196
Director deferred stock units	—		—		780		720
Performance stock units	809		479		3,095		1,576
Total	$	2,675	$	2,796	$	10,693	$	9,556
Income tax benefit	$	452	$	587	$	1,768	$	2,007

Unrecognized Stock-Based Compensation Expense

Unrecognized stock-based compensation expense at September 30, 2019 is presented in the table below. Unrecognized stock-based compensation expense related to performance stock units is presented assuming attainment of the maximum payout rate as set forth by the performance criteria.

Stock options	$	96
Non-vested stock awards/stock units	11,196
Performance stock units	3,432
Total	$	14,724