Stock compensation plans

We maintain a stock award plan for both employees and non-employee directors. The plan provides for the grant of a variety of equity awards, including options (generally non-qualified options), restricted shares, restricted share units ("RSUs"), and performance shares to key employees (as determined by the Compensation and Management Development Committee of the Board of Directors) for periods not to exceed ten years. Non-employee directors are awarded an annual distribution of common shares. Options granted to employees generally vest incrementally over four years and are generally exercisable for ten years from the vest date. RSUs represent the right to receive an equal number of common shares and are converted into common shares upon distribution. Restricted shares and RSUs generally cliff vest after three years. Both restricted share and RSU holders receive cash dividends during the vesting period. Performance shares vest upon attainment of the stated performance targets and minimum service requirements and are converted into common shares upon distribution. As of December 31, 2017, there were 25.0 million shares that remained available for grant under the plan. Our stock compensation expense for the three years ended December 31, 2017, is presented below ($000's omitted):



	2017		2016		2015
Stock options	$	—	$	—	$	37
Restricted shares (including RSUs and performance shares)	24,207		18,626		16,852
Long-term incentive plans	9,476		3,602		7,863
	$	33,683	$	22,228	$	24,752

Stock options

A summary of stock option activity for the three years ended December 31, 2017, is presented below (000’s omitted, except per share data):



	2017					2016					2015
	Shares			Weighted- Average Per Share Exercise Price		Shares			Weighted- Average Per Share Exercise Price		Shares			Weighted- Average Per Share Exercise Price
Outstanding, beginning of year	3,623			$	12	6,040			$	19	9,370			$	23
Granted	—			—		—			—		—			—
Exercised	(2,353		)	12		(498		)	12		(904		)	12
Forfeited	(102		)	28		(1,919		)	34		(2,426		)	37
Outstanding, end of year	1,168			$	11	3,623			$	12	6,040			$	19
Options exercisable at year end	1,168			$	11	3,623			$	12	6,040			$	19
Weighted-average per share fair value of options granted during the year	$	—				$	—				$	—

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



	Options Outstanding				Options Exercisable
	Number Outstanding (000's omitted)	Weighted- Average Remaining Contract Life (in years)	Weighted- Average Per Share Exercise Price		Number Exercisable (000's omitted)	Weighted- Average Per Share Exercise Price
$0.01 to $10.00	264	2.9	$	8	264	$	8
$10.01 to $20.00	904	1.6	12		904	12
	1,168	1.9	$	11	1,168	$	11

We did not issue any stock options during 2017, 2016, or 2015. As a result, there is no unrecognized compensation cost related to stock option awards at December 31, 2017. The intrinsic value of a stock option is the amount by which the market value of the underlying stock exceeds the exercise price of the option. The aggregate intrinsic value of stock options that were exercised during 2017, 2016, and 2015 was $31.1 million, $4.5 million, and $9.4 million, respectively. As of December 31, 2017, options outstanding, all of which were exercisable, had an intrinsic value of $25.8 million.

Restricted shares (including RSUs and performance shares)

A summary of restricted share activity, including RSUs and performance shares, for the three years ended December 31, 2017, is presented below (000’s omitted, except per share data):



	2017				2016				2015
	Shares		Weighted- Average Per Share Grant Date Fair Value		Shares		Weighted- Average Per Share Grant Date Fair Value		Shares		Weighted- Average Per Share Grant Date Fair Value
Outstanding, beginning of year	2,974		$	19	2,576		$	18	2,890		$	15
Granted	1,251		21		1,853		17		932		22
Distributed	(775	)	19		(546	)	20		(1,090	)	10
Forfeited	(179	)	19		(909	)	12		(156	)	19
Outstanding, end of year	3,271		$	19	2,974		$	19	2,576		$	18
Vested, end of year	152		$	17	123		$	15	89		$	14

During 2017, 2016, and 2015, the total fair value of shares vested during the year was $15.0 million, $11.0 million, and $10.2 million, respectively. Unamortized compensation cost related to restricted share awards was $18.6 million at December 31, 2017. These costs will be expensed over a weighted-average period of approximately 2 years. Additionally, there were 152,472 RSUs outstanding at December 31, 2017, that had vested but had not yet been paid out because the payout date had been deferred by the holders.

Long-term incentive plans

We maintain long-term incentive plans for senior management and other employees that provide awards based on the achievement of stated performance targets over three-year periods. Awards are stated in dollars but are settled in common shares based on the stock price at the end of the performance period. If the share price falls below a floor of $5.00 per share at the end of the performance period or we do not have a sufficient number of shares available under our stock incentive plans at the time of settlement, then a portion of each award will be paid in cash. We adjust the liabilities and recognize the expense associated with the awards based on the probability of achieving the stated performance targets at each reporting period. Liabilities for these awards totaled $14.0 million and $11.2 million at December 31, 2017 and 2016, respectively.