Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2020

Share-based Payment Arrangement [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 June 30, 2020, there were 1,108,516 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, 2020	55,370	$	74.76	440,647	$	90.22	177,288	$	83.48	1,980,866	$	64.60
Authorized	—	—		—	—		—	—		—	—
Granted	10,428	73.84		458	65.43		—	—		—	—
Exercised/vested	(12,938)	71.09		—	—		(41,755)	69.70		(88,830)	54.56
Forfeited/expired	—	—		(1,840)	89.29		(6,894)	81.33		(5,052)	76.19
Balance, June 30, 2020	52,860	$	75.47	439,265	$	90.20	128,639	$	88.07	1,886,984	$	65.04

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 June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
New shares issued from available authorized shares	—		—		—		—
Issued from available treasury stock	77,303		53,035		143,523		153,900
Total	77,303		53,035		143,523		153,900
Proceeds from stock option exercises	$	3,383	$	2,956	$	4,846	$	7,841

Share-based Payment Arrangement, Cost by Plan [Table Text Block]

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Stock options	$	—	$	379	$	—	$	761
Non-vested stock awards/stock units	2,062		2,056		4,326		4,191
Director deferred stock units	770		780		770		780
Performance stock units	440		1,149		688		2,286
Total	$	3,272	$	4,364	$	5,784	$	8,018
Income tax benefit	$	624	$	732	$	1,089	$	1,316

Unrecognized Stock-Based Compensation Expense

Unrecognized stock-based compensation expense at June 30, 2020 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.

Non-vested stock awards/stock units	$	14,425
Performance stock units	5,096
Total	$	19,521