Share-Based Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of share-based compensation expense

A summary of share-based compensation expense included in net income is as follows:

	Year Ended December 31,
	2017			2016			2015
	(In thousands)
Grants of common shares and options	$	12,371		$	11,227		$	12,074
Capitalized share-based compensation	(1,385		)	(1,310		)	(868		)
Share-based compensation expense	$	10,986		$	9,917		$	11,206

Summary of weighted average assumptions used to value options granted

The following table provides a summary of the weighted-average assumption used to value options granted in 2016:

Volatility	18.8	%
Expected dividend yield	2.8	%
Expected term (in years)	6.0
Risk free interest rate	1.5	%

Summary of option activity

The following table provides a summary of option activity for 2017:

	Shares Under Option		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
					(In years)	(In thousands)
Outstanding at December 31, 2016	259,119		$	56.66
Granted	—		—
Exercised	(152,634	)	65.37
Forfeited or expired	—		—
Outstanding at December 31, 2017	106,485		$	44.18	1.2	$	9,451
Exercisable at December 31, 2017	105,939		$	43.62	1.1	$	9,451

Summary of restricted share activity

The following table provides a summary of restricted share activity for 2017:

	Shares		Weighted-Average Grant-Date Fair Value
Unvested at December 31, 2016	217,353		$	142.70
Granted	109,815		139.31
Vested	(87,704	)	131.55
Forfeited	(2,293	)	142.09
Unvested at December 31, 2017	237,171

Schedule of common shares awarded under various compensation plans

Subsequent to December 31, 2017, common shares were awarded under various compensation plans as follows:

Date	Award		Vesting Term	Beneficiary
January 2, 2018	5,416	Shares	Immediate	Trustees
February 7, 2018	92,552	Restricted shares	3-4 years	Officers and key employees
February 7, 2018	488	Options	5 years	Officers and key employees