Stock Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2015

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

Summary of employee restricted common stock grant awards

The following table summarizes employee restricted common stock grant awards by year for grant years with unvested shares outstanding at December 31, 2015 and the remaining vesting schedule.

	2015	2014		2013		2012	2011
Number of shares of restricted common stock:
Granted during the year	401,520	482,001		494,420		155,000	663,530
Unvested at December 31, 2015	170,390	63,427		—		—	65,000
Scheduled to vest during the year ending:
December 31, 2016	44,020	35,040	(2)	—	(2)	—	65,000	(1)
December 31, 2017	126,370	28,387		—		—	—

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(1) Shares of restricted common stock granted under a performance-based award which will vest on June 30, 2016 if the performance conditions are met.

(2) In December 2015, vesting conditions were accelerated for the remaining 2013 and certain 2014 restricted common stock grant awards, totaling 200,797 shares, otherwise scheduled to vest in 2016.

Summary of restricted stock units awarded

The following table summarizes restricted stock units awarded by year for grant years with unvested units outstanding at December 31, 2015.

	2015		2014		2013
Number of shares of restricted stock units:
Granted during the year		409,800		395,900		432,300
Unvested at December 31, 2015		400,600		350,900		—	(1)
Vest date	February 1, 2018		February 1, 2017		February 1, 2016
Performance measurement period:
Fiscal year ended	December 31, 2017		December 31, 2016		December 31, 2015

______________________________

(1) In December 2015 vesting conditions for the remaining 366,400 shares of the 2013 restricted stock units granted were deemed to have been achieved.

Summary of restricted common stock and performance-based restricted stock unit activity

The following table summarizes restricted common stock and performance-based restricted stock unit activity in our stock incentive plans for the year ended December 31, 2015.

	Restricted Common Stock						Restricted Stock Units
	Number of Shares		Weighted Average Grant Date Fair Value				Number of Units		Weighted Average Grant Date Fair Value
Unvested at beginning of year	752,701			$	11.90		776,500			$	10.66
Granted	429,752			13.05			409,800			12.64
Vested	(741,690	)	(1)	(12.18		)	(366,400	)	(2)	(9.22		)
Forfeited	(65,946	)		(11.77		)	(68,400	)		(11.03		)
Unvested at end of year	374,817			12.68			751,500			12.41

(1) Includes 200,797 shares originally scheduled to vest at various times during 2016 that had a compensation expense of $2.4 million.

(2) Shares originally scheduled to vest in February 2016.

Summary of option activity

The following table summarizes option activity in our stock incentive plans for the year ended December 31, 2015.

	Number of Options		Weighted Average Exercise Price
Outstanding at beginning of year	36,000			$	28.58
Expired	(24,000	)		(27.99		)
Outstanding and exercisable at end of year	12,000			29.76