Equity Incentive Plan

All grants of common shares and options to purchase common shares were issued under the Company's 2007 Equity Incentive Plan prior to May 12, 2016 and under the 2016 Equity Incentive Plan on and after May 12, 2016. Under the 2016 Equity Incentive Plan, an aggregate of 1,950,000 common shares, options to purchase common shares and restricted share units, subject to adjustment in the event of certain capital events, may be granted. At December 31, 2017, there were 1,631,841 shares available for grant under the 2016 Equity Incentive Plan.

Share Options

Share options granted under the 2007 Equity Incentive Plan and the 2016 Equity Incentive Plan have exercise prices equal to the fair market value of a common share at the date of grant. The options may be granted for any reasonable term, not to exceed 10 years, and for employees typically become exercisable at a rate of 25% per year over a four-year period. The Company generally issues new common shares upon option exercise. A summary of the Company’s share option activity and related information is as follows:



	Number of shares		Option price per share					Weighted avg. exercise price
Outstanding at December 31, 2014	950,214		$	18.18	—	$	65.50	$	42.48
Exercised	(476,400	)	18.18		—	61.53		37.42
Granted	121,546		61.79		—	61.79		61.79
Forfeited	(79,055	)	45.20		—	65.50		63.88
Outstanding at December 31, 2015	516,305		$	19.02	—	$	65.50	$	48.42
Exercised	(230,319	)	19.41		—	65.50		44.05
Outstanding at December 31, 2016	285,986		$	19.02	—	$	61.79	$	51.93
Exercised	(29,253	)	46.86		—	61.79		54.54
Granted	2,215		76.63		—	76.63		76.63
Forfeited/Expired	(1,342	)	51.64		—	61.79		59.52
Outstanding at December 31, 2017	257,606		$	19.02	—	$	76.63	$	51.81

The weighted average fair value of options granted was $7.91 and $16.35 during 2017 and 2015, respectively. There were no options granted during 2016. The intrinsic value of stock options exercised was $0.5 million, $5.2 million, and $7.3 million during the years ended December 31, 2017, 2016 and 2015, respectively. Additionally, the Company repurchased 22,076 shares into treasury shares in conjunction with the stock options exercised during the year ended December 31, 2017 with a total value of $1.6 million.

The expense related to share options included in the determination of net income for the years ended December 31, 2017, 2016 and 2015 was $0.7 million, $0.9 million, and $2.5 million (including $1.4 million included in retirement severance expense in the accompanying consolidated statement of income), respectively. The following assumptions were used in applying the Black-Scholes option pricing model at the grant dates: risk-free interest rate of 2.1% and 1.9% in 2017 and 2015, respectively, dividend yield of 5.4% and 5.9% in 2017 and 2015, respectively, volatility factors in the expected market price of the Company’s common shares of 22.0% and 48.0% in 2017 and 2015, respectively, 0.74% and 0.78% expected forfeiture rates for 2017 and 2015, and an expected life of approximately six years for 2017 and 2015. The Company uses historical data to estimate the expected life of the option and the risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. Additionally, expected volatility is computed based on the average historical volatility of the Company’s publicly traded shares.

At December 31, 2017, stock-option expense to be recognized in future periods was as follows (in thousands):



	Amount
Year:
2018	$	291
2019	4
2020	4
Total	$	299

The following table summarizes outstanding options at December 31, 2017:



Exercise price range	Options outstanding	Weighted avg. life remaining	Weighted avg. exercise price		Aggregate intrinsic value (in thousands)
$ 19.02 - 19.99	11,097	1.4
20.00 - 29.99	—	—
30.00 - 39.99	1,428	2.0
40.00 - 49.99	86,041	4.1
50.00 - 59.99	75,939	5.8
60.00 - 69.99	80,886	7.1
70.00 - 76.63	2,215	9.1
	257,606	5.5	$	51.81	$	3,541

The following table summarizes exercisable options at December 31, 2017:



Exercise price range	Options outstanding	Weighted avg. life remaining	Weighted avg. exercise price		Aggregate intrinsic value (in thousands)
$ 19.02 - 19.99	11,097	1.4
20.00 - 29.99	—	—
30.00 - 39.99	1,428	2.0
40.00 - 49.99	86,041	4.1
50.00 - 59.99	51,276	5.7
60.00 - 61.79	38,225	7.1
70.00 - 76.63	—	—
	188,067	5.0	$	49.28	$	3,044

Nonvested Shares

A summary of the Company’s nonvested share activity and related information is as follows:



	Number of shares		Weighted avg. grant date fair value		Weighted avg. life remaining
Outstanding at December 31, 2016	534,317		$	59.22
Granted	296,914		76.49
Vested	(209,767	)	57.47
Forfeited	(1,342	)	66.88
Outstanding at December 31, 2017	620,122		$	68.07	0.96

The holders of nonvested shares have voting rights and receive dividends from the date of grant. These shares vest ratably over a period of three to four years. The fair value of the nonvested shares that vested was $15.1 million, $9.2 million, and $17.1 million (including $6.7 million related to the vesting of shares for the Company's former Chief Executive Officer) for the years ended December 31, 2017, 2016 and 2015, respectively. At December 31, 2017, unamortized share-based compensation expense related to nonvested shares was $21.2 million and will be recognized in future periods as follows (in thousands):



	Amount
Year:
2018	$	10,391
2019	7,337
2020	3,445
Total	$	21,173

Restricted Share Units

A summary of the Company’s restricted share unit activity and related information is as follows:



	Number of Shares		Weighted Average Grant Date Fair Value		Weighted Average Life Remaining
Outstanding at December 31, 2016	15,805		$	70.93
Granted	19,030		70.91
Vested	(15,805	)	70.93
Outstanding at December 31, 2017	19,030		$	70.91	0.33

The holders of restricted share units have voting rights and receive dividends from the date of grant. The share units vest upon the earlier of the day preceding the next annual meeting of shareholders or a change of control. The settlement date for the shares is selected by the non-employee trustee, and ranges from one year from the grant date to upon termination of service. At December 31, 2017, unamortized share-based compensation expense related to restricted share units was $450 thousand which will be recognized in 2018.