Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2019

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary Of PSU Transactions

	Number	Weighted
	of	Average
	Share Units	Fair Value
Nonvested share units at beginning of period	443,410	$	27.20
Granted	-		-
Performance criteria adjustment	(66,658)		33.43
Forfeited	(9,130)		33.19
Share units issued	(89,324)		52.32
Nonvested share units at end of period	278,298		17.43

Summary Of RSU Transactions

	Number	Weighted
	of	Average
	Stock Units	Fair Value
Nonvested stock units at beginning of period	130,085	$	33.13
Granted	55,686		36.01
Stock units vested and issued	(40,971)		32.89
Forfeited	(4,398)		35.26
Nonvested stock units at end of period	140,402		34.28

Assumptions Used In The Pricing Model

	2019		2018
Expected term (years)		5.47		5.46
Risk-free interest rate		2.53%		2.72%
Expected volatility		17.7%		17.2%
Dividend yield		2.44%		2.37%
Grant date fair value per option	$	5.25	$	5.10

Summary Of Stock Option Transactions

		Weighted		Weighted
		Average		Average	Aggregate
		Exercise		Remaining	Intrinsic
	Shares	Price		Life (years)	Value
Outstanding at beginning of period	422,972	$	25.97
Granted	769,115		35.94
Forfeited	(34,158)		35.46
Expired / Cancelled	(2,185)		32.22
Exercised	(108,491)		15.99
Outstanding at end of period	1,047,253	$	34.00	8.6	$	11,337
Exercisable at end of period	175,279	$	26.14	5.4	$	3,275

Performance Share Units [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary Of Compensation Costs

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2019		2018		2019		2018
Stock-based compensation within operations and maintenance expenses	$	584	$	1,087	$	2,434	$	3,286
Income tax benefit		166		303		682		917

Restricted Stock Units [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary Of Compensation Costs

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2019		2018		2019		2018
Stock-based compensation within operations and maintenance expenses	$	395	$	493	$	1,231	$	1,199
Income tax benefit		112		140		348		341

Stock Options [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary Of Compensation Costs

	Three Months Ended				Nine Months Ended
	September 30,					September 30,
	2019		2018		2019		2018
Stock-based compensation within operations and maintenance expenses	$	637	$	159	$	1,625	$	407
Income tax benefit		180		45		458		145

Stock Awards [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary Of Compensation Costs

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2019		2018		2019		2018
Stock-based compensation within operations and maintenance expenses	$	158	$	160	$	540	$	440
Income tax benefit		46		46		156		127

Summary Of Nonvested Share Activity

	Number	Weighted
	of	Average
	Stock Awards	Fair Value
Nonvested stock awards at beginning of period	-	$	-
Granted	13,368		40.41
Vested	(13,368)		40.41
Nonvested stock awards at end of period	-		-