Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Schedules of Executive Management Share-based Compensation Activity

Information with respect to these plans is presented below:

	Number of shares	Weighted average grant date value per share		Year-end intrinsic value (000's)
Shares potentially payable at January 1, 2018	157,405	$	40.30	$	6,343
Forfeitures	—	$	—
Payments	(79,762)	$	39.90
Shares accrued based on 2018 performance	34,822	$	70.59
Shares potentially payable at December 31, 2018	112,465	$	49.96	$	5,619
Forfeitures	—
Payments	(45,689)	$	36.74
Shares accrued based on 2019 performance	14,936	$	92.12
Shares potentially payable at December 31, 2019	81,712	$	65.06	$	5,316
Forfeitures	—	$	—
Payments	(20,680)	$	47.35
Shares accrued based on 2020 performance	36,808	$	73.43
Shares potentially payable at December 31, 2020	97,840	$	71.95	$	7,040

Schedules of Other Share-based Compensation Activity

The determination of compensation expense for other management share-based compensation plans is based on the number of outstanding share units, the end-of-period share price, and Company performance. Information with respect to these plans is presented below:

	Number of shares	Weighted average value per share		Cash paid for share based liabilities (000's)
Share units potentially payable at January 1, 2018	236,096
Grants	65,370
Changes due to performance	14,343
Payments	(75,545)	$	62.69	$	4,736
Forfeitures	(12,963)
Share units potentially payable at December 31, 2018	227,301
Grants	58,878
Changes due to performance	21,740
Payments	(69,912)	$	70.67	$	5,528
Forfeitures	(22,935)
Share units potentially payable at December 31, 2019	215,072
Grants	63,104
Changes due to performance	27,921
Payments	(80,808)	$	73.04	$	5,848
Forfeitures	(11,441)
Share units potentially payable at December 31, 2020	213,848