Equity Incentive Plan

All grants of common shares and options to purchase common shares are issued under the Company's 2007 Equity Incentive Plan and an aggregate of 3,650,000 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 March 31, 2016, there were 766,007 shares available for grant under the 2007 Equity Incentive Plan.

Share Options

Share options granted under the 2007 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, 2015	516,305		$	19.02	—	$	65.50	$	48.42
Exercised	(88,294	)	19.41		—	61.79		30.51
Outstanding at March 31, 2016	428,011		$	19.02	—	$	65.50	$	52.11

There were no options granted during the three months ended March 31, 2016. The weighted average fair value of options granted was $16.35 during the three months ended March 31, 2015. The intrinsic value of stock options exercised was $2.8 million and $0.2 million for the three months ended March 31, 2016 and 2015, respectively. Additionally, the Company repurchased 53,687 shares into treasury shares in conjunction with the stock options exercised during the three months ended March 31, 2016 with a total value of $3.3 million. At March 31, 2016, stock-option expense to be recognized in future periods was $1.6 million.

The expense related to share options included in the determination of net income for the three months ended March 31, 2016 and 2015 was $0.2 million and $1.7 million (including $1.4 million included in retirement severance expense in the accompanying consolidated statements of income), respectively. The following assumptions were used in applying the Black-Scholes option pricing model at the grant dates for the three months ended March 31, 2015: risk-free interest rate of 1.9%, dividend yield of 5.9%, volatility factors in the expected market price of the Company’s common shares of 48.0%, 0.78% expected forfeiture rate and an expected life of approximately six years. 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.

The following table summarizes outstanding options at March 31, 2016:



Exercise price range	Options outstanding	Weighted avg. life remaining	Weighted avg. exercise price		Aggregate intrinsic value (in thousands)
$ 19.02 - 19.99	11,097	3.1
20.00 - 29.99	—	—
30.00 - 39.99	2,625	3.8
40.00 - 49.99	175,166	5.0
50.00 - 59.99	106,275	7.3
60.00 - 65.50	132,848	6.2
	428,011	5.9	$	52.11	$	6,210

The following table summarizes exercisable options at March 31, 2016:



Exercise price range	Options outstanding	Weighted avg. life remaining	Weighted avg. exercise price		Aggregate intrinsic value (in thousands)
$ 19.02 - 19.99	11,097	3.1
20.00 - 29.99	—	—
30.00 - 39.99	2,625	3.8
40.00 - 49.99	155,636	4.8
50.00 - 59.99	52,259	6.9
60.00 - 65.50	66,863	3.5
	288,480	4.8	$	50.24	$	4,726

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, 2015	390,441		$	54.84
Granted	300,752		61.53
Vested	(156,767	)	52.73
Forfeited	—		—
Outstanding at March 31, 2016	534,426		$	59.22	1.77

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 $9.2 million and $17.1 million (including $6.7 million in retirement severance expense in the accompanying consolidated statements of income) for the three months ended March 31, 2016 and 2015, respectively. At March 31, 2016, unamortized share-based compensation expense related to nonvested shares was $23.2 million.

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, 2015	18,036	$	57.57
Granted	—	—
Vested	—	—
Outstanding at March 31, 2016	18,036	$	57.57	0.12

The holders of restricted share units receive dividend equivalents 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 March 31, 2016, unamortized share-based compensation expense related to restricted share units was $87 thousand.