Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of Share-Based Compensation Expense

The following table summarizes share-based compensation expense recognized for the periods presented:

	Year Ended December 31,
	2015			2014		2013
Equity-classified awards:
Stock option awards	$	1,704		$	1,598	$	3,123
Common, deferred, restricted and restricted unit awards	2,836			2,029		2,658
	4,540			$	3,627	$	5,781
Liability-classified awards	(711		)	4,520		4,116
	$	3,829		$	8,147	$	9,897

Fair Value of Each Option Award Estimated on Date of Grant Using Black-Scholes-Merton Option-Pricing Formula

The fair value of each option award is estimated on the date of grant using the Black-Scholes-Merton option-pricing formula that uses the assumptions noted in the following table. Expected volatilities are based on historical changes in the market value of our stock. Separate groups of employees that have similar historical exercise behavior are considered separately to estimate expected lives. Options granted have a maximum term of ten years. We base the risk-free interest rate on the U.S. Treasury rate for the week of the grant having a term equal to the expected life of the option. 

	2015	2014	2013
Expected volatility	64.6% to 69.4%	56.2% to 63.7%	56.9% to 70.1%
Dividend yield	0.00% to 0.00%	0.00% to 0.00%	0.00% to 0.00%
Expected life	3.5 to 4.6 years	3.5 to 4.6 years	3.5 to 4.6 years
Risk-free interest rate	0.87% to 1.54%	0.82% to 1.63%	0.34% to 0.58%

Activity of Awarded Options

The following table summarizes activity for our most recent fiscal year with respect to stock options: 

	Shares Under Options		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
Outstanding at beginning of year	3,094,016		$	16.89
Granted	459,087		6.03
Exercised	—		—
Forfeited or expired	(469,282	)	11.75
Outstanding at end of year	3,083,821		$	16.05	5.4	$	—
Exercisable at end of year	2,416,073		$	18.28	4.6	$	—

Activity of Awarded Deferred Common Stock Units

The following table summarizes activity for our most recent fiscal year with respect to awarded deferred common stock units: 

	Deferred Common Stock Units		Weighted-Average Grant Date Fair Value
Balance at beginning of year	253,879		$	12.81
Granted	195,395		1.33
Converted	(1,776	)	16.89
Balance at end of year	447,498		$	7.75

Restricted Stock Units (RSUs)

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Activity of Awarded Restricted Stock Units

The following table summarizes activity for our most recent fiscal year with respect to awarded restricted stock units:

	Restricted Stock Units		Weighted-Average Grant Date Fair Value
Balance at beginning of year 1	599,347		$	7.93
Granted	544,030		5.07
Vested	(422,504	)	5.13
Forfeited	(251,887	)	8.24
Balance at end of year 1	468,986		$	6.97

_____________________

¹Excludes 346,777 units at the beginning of the year and 346,777 units at the end of year that have vested due to retirement eligibility, but have not yet been settled or converted to common shares.

Performance Based Restricted Stock Units (PBRSUs)

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of Share-based Payment Award, Equity Instruments Other than Options, Valuation Assumptions

The ranges for the assumptions used in the Monte Carlo model for the PBRSUs granted in 2015, 2014 and 2013 are as follows:

	2015	2014	2013
Expected volatility	66.5% to 97.7%	52.6% to 72.3%	51.3% to 66.7%
Dividend yield	0.0% to 0.0%	0.0% to 0.0%	0.0% to 0.0%
Risk-free interest rate	0.01% to 1.31%	0.02% to 1.07%	0.01% to 0.78%

Activity of Awarded Performance-based RSUs

The following table summarizes activity for our most recent fiscal year with respect to PBRSUs:

	Performance-Based Restricted Stock Units	Weighted-Average Fair Value
Balance at beginning of year	658,916	$	16.29
Granted	282,181	7.38
Forfeited	—	—
Balance at end of year	941,097	$	9.19