The Company’s shareholders have approved various equity incentive plans, including the Amended and Restated 2009 Equity Incentive Plan (the “Legacy Plan”), the 2014 Long Term Incentive Plan (“2014 LTIP”), and the 2014 Non-Employee Director Incentive Plan (“2014 Director Plan”) (collectively, the “Plans”). All awards issued under the Plans are issued at the discretion of the Board of Directors. Under the Legacy Plan, employees received non-qualified stock options. Options are outstanding under the Legacy Plan; however, no additional awards may be granted.

Employees are eligible to receive non-qualified stock options, incentive stock options, share appreciation rights, performance shares, restricted shares, RSUs, and other awards under the 2014 LTIP. The maximum number of shares available for issuance under the 2014 LTIP is 4,171,150, and at December 31, 2019, 1,575,359 shares are available for grant.

Non-employee directors of the Company are eligible to receive non-qualified stock options, share appreciation rights, performance shares, restricted shares, RSUs, and other awards under the 2014 Director Plan. At the 2019 Annual General Meeting of Shareholders of the Company held on April 30, 2019, the Company's shareholders approved an amendment to the 2014 Director Plan. The Board of Directors of the Company had previously approved the amendment. The amendment increased the number of the Company's common shares authorized for issuance under the 2014 Director Plan by 100,000 shares. The maximum number of shares available for issuance under the 2014 Director Plan is 150,000, and at December 31, 2019, 108,594 shares are available for grant.

Generally, awards issued under the 2014 LTIP and 2014 Director Plan vest immediately in the event that an award recipient is terminated without Cause (as defined), and in the case of the 2014 LTIP for Good Reason (as defined), at any time following a Change in Control (as defined in the applicable plans).



	Year Ended December 31,
	2019				2018				2017
	Shares		Weighted- Average Exercise Price		Shares		Weighted- Average Exercise Price		Shares		Weighted- Average Exercise Price
Outstanding:
Beginning of year	1,115,324		$	29.02	1,479,236		$	27.81	2,234,699		$	22.84
Granted	—		$	—	—		$	—	205,244		$	42.24
Exercised	(459,415	)	$	26.87	(308,025	)	$	22.01	(898,218	)	$	18.53
Forfeited	(12,058	)	$	36.84	(55,887	)	$	35.69	(62,489	)	$	30.80
End of year	643,851		$	30.41	1,115,324		$	29.02	1,479,236		$	27.81
Exercisable, end of year	590,340		$	29.34	814,421		$	26.46	846,371		$	22.35

All of the outstanding options vest over three years and have a contractual life of seven years from the original date of grant. All of the outstanding options have an exercise price equal to the fair value of the underlying shares at the date of grant.

The intrinsic value of each option is determined based on the difference between the fair value of the underlying share and the exercise price of the underlying option. The total intrinsic value of options exercised during 2019, 2018 and 2017 was $8.2 million, $4.6 million and $20.4 million, respectively. The aggregate intrinsic value of options outstanding at December 31, 2019, 2018 and 2017 was $7.1 million, $9.4 million and $18.5 million, respectively. The aggregate intrinsic value of options exercisable at December 31, 2019, 2018 and 2017 was $7.1 million, $8.5 million and $14.9 million, respectively. The fair value used for calculating intrinsic values was $41.21, $36.54 and $40.01 at December 31, 2019, 2018 and 2017, respectively.

The weighted-average remaining contractual life of the options outstanding and options exercisable at December 31, 2019 is 2.9 years and 2.8 years, respectively. There were no options granted in 2019 or 2018. The weighted-average fair value of options granted during 2017 was $8.21. The value of the options granted was estimated at the date of grant using the Black-Scholes-Merton option pricing model using the following assumptions:

The risk-free interest rate assumption is based on the five-year U.S. Treasury rate at the date of the grant. The dividend yield assumption was based upon dividends expected to be declared over the life of the options at the date of grant. The share price volatility assumption was based upon the Company's 100-day realized volatility. The expected life is determined using the simplified method, which factors in the average of the midpoint and the contractual term of each tranche in determining a single expected life. The simplified method is used as the Company does not have sufficient historical exercise data to estimate an expected term.

The Black-Scholes-Merton option pricing model was developed for use in estimating the fair value of traded options that have no vesting restrictions and are fully transferable. In addition, option valuation models require the input of highly subjective assumptions including expected share price volatility. Because the Company’s share options have characteristics significantly different from those of traded options and because changes in the subjective input assumptions can materially affect the fair value estimate, the existing models do not necessarily provide a reliable single measure of the fair value of such share options.



	Year Ended December 31,
	2019				2018				2017
	Shares		Weighted- Average Grant Date Fair Value		Shares		Weighted- Average Grant Date Fair Value		Shares		Weighted- Average Grant Date Fair Value
Unvested, beginning of year	300,142		$	39.22	178,882		$	37.93	196,800		$	24.38
Granted	197,078		$	42.56	227,481		$	39.74	137,034		$	42.20
Vested	(134,407	)	$	37.99	(83,384	)	$	37.61	(132,764	)	$	24.24
Forfeited	(22,445	)	$	41.32	(22,837	)	$	40.21	(22,188	)	$	26.06
Unvested, end of year	340,368		$	41.50	300,142		$	39.22	178,882		$	37.93

The vesting period of RSUs granted to employees range from one to five years and vest ratably over the respective vesting period, with the majority vesting in three years. All RSUs granted to date to non-employee directors had a one year vesting period. The total fair value of shares vested in 2019, 2018 and 2017 was $5.3 million, $3.2 million and $5.5 million, respectively. The holders of RSUs are entitled to dividend equivalents. The dividend equivalents are settled in cash at the same time that the underlying RSUs vest and are subject to the same risk of forfeiture as the underlying shares. The fair value of the RSUs granted is based on the market price of the underlying shares.

Share based compensation expense is recognized on a straight line basis over the vesting period. The amount of expense and related tax benefit is summarized below:



	Year Ended December 31,
	2019		2018		2017
	(in thousands)
Share based compensation expense	$	7,178	$	6,228	$	7,688
U.S. tax benefit on share based compensation expense	$	872	$	716	$	2,093

As of December 31, 2019, the Company had $8.6 million of unrecognized share based compensation expense expected to be charged to earnings over a weighted-average period of 1.7 years.