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Equity Incentive Plan (Tables)

12 Months Ended

Dec. 31, 2020

Equity Incentive Plan

Schedule of restricted share activity

​

​	​	​	​	​	​
​		Shares		Weighted Average
​	​	Outstanding	​	Grant Date
​	​	(in thousands)	​	Fair Value
Unvested restricted stock at December 31, 2017		227	​	$	39.47
​	​	​	​	​	​
Restricted stock granted		57	​	$	48.85
Restricted stock vested		(71)	​	$	36.06
Restricted stock forfeited		(1)	​	$	48.28
​	​	​	​	​	​
Unvested restricted stock at December 31, 2018		212	​	$	42.74
​	​	​	​	​	​
Restricted stock granted		54	​	$	65.85
Restricted stock vested		(70)	​	$	39.55
Restricted stock forfeited		(2)	​	$	54.08
​	​	​	​	​	​
Unvested restricted stock at December 31, 2019		194	​	$	50.71
​	​	​	​	​	​
Restricted stock granted		52	​	$	78.43
Restricted stock vested	​	(68)	​	$	45.78
Restricted stock forfeited		(3)	​	$	63.80
​	​	​	​	​	​
Unvested restricted stock at December 31, 2020		175	​	$	60.53

Schedule of valuation assumptions used

​

​	​	​	​	​	​	​	​	​	​	​
Year Ended December 31,	​	​	2020		​	2019		​	2018
​	​	​	​	​	​	​	​	​	​	​
Expected term (years)	​	​	2.9	​	​	2.9	​	​	2.9	​
Volatility	​	​	18.4	%	​	19.7	%	​	19.1	%
Dividend yield	​	​	2.9	%	​	3.4	%	​	4.4	%
Risk-free rate	​	​	1.3	%	​	2.5	%	​	2.4	%

Schedule of performance share and unit activity

​

​	​	​	​	​	​
​		Target Number		Weighted Average
​	​	of Awards	​	Grant Date
​	​	(in thousands)	​	Fair Value
Performance shares at December 31, 2017		—	​	$	—
​	​	​	​	​	​
Performance shares granted	​	31	​	$	55.29
​	​	​	​	​	​
Performance shares at December 31, 2018		31	​	$	55.29
​	​	​	​	​	​
Performance shares granted	​	30	​	$	66.96
​	​	​	​	​	​
Performance units and shares at December 31, 2019		61	​	$	61.04
​	​	​	​	​	​
Performance units granted		26	​	$	90.17
​	​	​	​	​	​
Performance units and shares at December 31, 2020	​	87	​	$	69.61
​		​	​	​	​

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