Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2017

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	476,896	$	27.96
Granted	125,679		30.79
Performance criteria adjustment	(58,533)		27.78
Forfeited	(10,046)		27.68
Share units vested in prior period and issued in current period	32,400		25.31
Share units issued	(125,999)		36.37
Nonvested share units at end of period	440,397	$	26.20

Summary Of RSU Transactions

	Number	Weighted
	of	Average
	Stock Units	Fair Value
Nonvested stock units at beginning of period	109,273	$	28.48
Granted	41,293		30.37
Stock units vested and issued	(26,279)		26.12
Forfeited	(1,541)		30.57
Nonvested stock units at end of period	122,746	$	29.59

Assumptions Used In The Pricing Model

	2017
Expected term (years)	5.45
Risk-free interest rate	2.01%
Expected volatility	17.7%
Dividend yield	2.51%
Grant date fair value per option	$       4.07

Summary Of Stock Option Transactions

		Weighted		Weighted
		Average		Average	Aggregate
		Exercise		Remaining	Intrinsic
	Shares	Price		Life (years)	Value
Outstanding at beginning of period	427,335	$	15.55
Granted	120,473		30.47
Forfeited	(121)		30.47
Expired / Cancelled	(2,812)		14.26
Exercised	(86,511)		17.76
Outstanding and exercisable at end of period	458,364	$	19.06	4.0	$	5,999

Performance Share Units [Member]

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

Summary Of Compensation Costs

	Three Months Ended
	March 31,
	2017		2016
Stock-based compensation within operations and maintenance expenses	$	870	$	525
Income tax benefit		353		209

Restricted Stock Units [Member]

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

Summary Of Compensation Costs

	Three Months Ended
	March 31,
	2017		2016
Stock-based compensation within operations and maintenance expenses	$	281	$	168
Income tax benefit		116		69

Stock Options [Member]

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

Summary Of Compensation Costs

	Three Months Ended
	March 31,
	2017		2016
Stock-based compensation within operations and maintenance expenses		30		-
Income tax benefit	$	92	$	216

Stock Compensation Plan [Member]

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

Summary Of Compensation Costs

	Three Months Ended
	March 31,
	2017		2016
Stock-based compensation within operations and maintenance expenses	$	131	$	112
Income tax benefit		54		47

Summary Of Nonvested Share Activity

	Number	Weighted
	of	Average
	Stock Awards	Fair Value
Nonvested stock awards at beginning of period	-	$	-
Granted	4,081		32.15
Vested	(4,081)		32.15
Nonvested stock awards at end of period	-	$	-