Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

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,
	2014		2013		2012
Equity-classified awards:
Stock option awards	$	1,598	$	3,123	$	4,424
Common, deferred, restricted and restricted unit awards	2,029		2,658		1,923
	3,627		$	5,781	$	6,347
Liability-classified awards	4,520		4,116		714
	$	8,147	$	9,897	$	7,061

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. 

	2014	2013	2012
Expected volatility	56.2% to 63.7%	56.9% to 70.1%	67.3% to 72.9%
Dividend yield	0.00% to 0.00%	0.00% to 0.00%	2.25% to 4.98%
Expected life	3.5 to 4.6 years	3.5 to 4.6 years	3.5 to 4.6 years
Risk-free interest rate	0.82% to 1.63%	0.34% to 0.58%	0.36% to 0.51%

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	3,129,069		$	16.15
Granted	367,016		16.15
Exercised	(257,347	)	5.55
Forfeited or expired	(144,722	)	19.24
Outstanding at end of year	3,094,016		$	16.89	6.0	$	2,005
Exercisable at end of year	2,221,701		$	19.90	5.0	$	907

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	217,708	$	13.01
Granted	36,171	11.61
Converted	—	—
Balance at end of year	253,879	$	12.81

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	500,850		$	4.42
Granted	191,483		16.32
Vested	(92,986	)	6.29
Forfeited	—		—
Balance at end of year 1	599,347		$	7.93

_____________________

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 2014, 2013 and 2012 are as follows:

	2014	2013	2012
Expected volatility	52.6% to 72.3%	51.3% to 66.7%	29.3% to 78.0%
Dividend yield	0.0% to 0.0%	0.0% to 0.0%	0.0% to 5.3%
Risk-free interest rate	0.02% to 1.07%	0.01% to 0.78%	0.02% to 0.43%

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	561,310	$	16.07
Granted	97,606	19.21
Forfeited	—	—
Balance at end of year	658,916	$	16.29