Share-Based Payments (Tables)

6 Months Ended

Jun. 30, 2016

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

Compensation Costs Related to Share-Based Payments

	Three months ended				Six months ended
	June 30,				June 30,
		2016		2015		2016		2015
Stock option compensation expense	$	1,400	$	1,333	$	2,470	$	2,056
Share unit expense:
Equity-classified PSUs		486		-		486		-
Liability-classified share units		5,508		2,902		6,780		3,919
Employee share purchase plan -
employer contributions		396		323		749		631
	$	7,790	$	4,558	$	10,485	$	6,606

Summary of Stock Option Activity

					WA
	Common			WA	remaining			Aggregate
	shares under			exercise	contractual			intrinsic
	option	price			life (in years)	value
Outstanding, December 31, 2014	3,897,791			22.09
Granted	880,706			25.50
Exercised	(1,412,535)			21.11			$	9,426
Forfeited	(89,884)			23.10
Outstanding, December 31, 2015	3,276,078			23.40
Granted	1,237,633			24.25
Exercised	(806,569)			22.39			$	5,774
Forfeited	(65,259)			24.32
Outstanding, June 30, 2016	3,641,883		$	23.90	7.8		$	35,992
Exercisable, June 30, 2016	1,433,078		$	22.84	5.8		$	15,675

Summary of Share Unit Activity

	Equity-classified awards			Liability-classified awards
	PSUs			PSUs (1)			Restricted share units			DSUs
		WA grant			WA grant			WA grant			WA grant
			date fair			date fair			date fair			date fair
	Number		value	Number		value	Number		value	Number		value
Outstanding, December 31, 2014	-	$	-	238,573	$	23.38	403,587	$	22.32	42,289	$	22.33
Granted	-		-	218,699		24.57	20,528		26.38	29,072		26.07
Vested and settled	-		-	(6,870)		22.22	(28,887)		22.53	(13,365)		22.34
Forfeited	-		-	(28,817)		23.23	(62,274)		21.56	-		-
Outstanding, December 31, 2015	-	$	-	421,585	$	24.03	332,954	$	22.70	57,996	$	24.21
Granted	5,288		29.66	248,910		23.32	3,033		25.92	9,714		26.08
Transferred to (from) equity
awards on modification	257,934		27.34	(257,934)		23.86	-		-	-		-
Vested and settled	-		-	(41,898)		22.17	(157,406)		22.11	(1,847)		25.28
Forfeited	-		-	(31,089)		22.65	(8,944)		22.61	-		-
Outstanding, June 30, 2016	263,222	$	27.39	339,574	$	23.99	169,637	$	23.31	65,863	$	24.45

Stock Option Plan [Member]

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

Summary of Stock Option and Performance Share Unit Pricing Assumptions

Six months ended June 30,	2016	2015
Risk free interest rate	1.2%	1.8%
Expected dividend yield	2.66%	2.18%
Expected lives of the stock options	5 years	5 years
Expected volatility	26.5%	26.3%

Senior Executive and Employee Performance Share Unit Plans [Member]

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

Summary of Stock Option and Performance Share Unit Pricing Assumptions

Six months ended June 30,	2016	2015
Risk free interest rate	1.2%	1.3%
Expected dividend yield	2.49%	2.17%
Expected lives of the PSUs	3 years	3 years
Expected volatility	29.9%	29.4%
Average expected volatility of comparable companies	37.0%	32.8%

Sign-on Grant Performance Share Unit Plans [Member]

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

Summary of Stock Option and Performance Share Unit Pricing Assumptions

Six months ended June 30,	2016	2015
Risk free interest rate	0.9%	1.5%
Expected dividend yield	2.31%	2.07%
Expected volatility	28.3%	35.2%