Stock-Based Compensation

The Company’s stock-based compensation expense for the three and six months ended June 30, 2015 and 2014 included performance-based restricted stock units ("PRSUs"), non-qualified stock options, restricted stock units ("RSUs") and deferred stock units ("DSUs"). A summary of the Company’s stock-based compensation expense is presented below:



(in millions)	Three Months Ended June 30,					Six Months Ended June 30,
	2015		2014			2015		2014
PRSU expense (benefit)	$	5.4	$	(0.9	)	$	7.4	$	0.2
Option expense	2.0		1.7			3.5		3.4
RSU/DSU expense	0.2		0.5			0.7		1.8
Total stock-based compensation expense	$	7.6	$	1.3		$	11.6	$	5.4

The Company recorded $4.0 million of accelerated amortization associated with the transition of the Company's former CEO for the three and six months ended June 30, 2015. The Company previously recognized $0.5 million in stock-based compensation expense for the six months ended June 30, 2015 associated with the PRSU and stock options granted in 2015 to the Company's former CEO.

The Company recorded a $3.0 million benefit in the accompanying Condensed Consolidated Statements of Income for the three and six months ended June 30, 2014, after re-evaluation of the probability of achieving certain financial goals related to PRSUs granted in 2013.

The Company uses the Black-Scholes option pricing model to calculate the fair value of stock options granted. The fair value of stock options granted was estimated using the Black-Scholes option pricing model with the following assumptions during the three and six months ended June 30, 2015 and 2014:



	Three months ended		Six months ended
	June 30,		June 30,
	2015	2014	2015	2014
Expected volatility range of stock	35.1% - 35.4%	58.3% - 66.5%	35.1% - 36.2%	58.3% - 66.5%
Expected life of option, range in years	3 - 5	2 - 4	3 - 5	2 - 4
Risk-free interest range rate	1.0% - 1.5%	0.4% - 1.2%	1.0% - 1.5%	0.4% - 1.2%
Expected dividend yield on stock	0.0% - 0.0%	0.6% - 0.7%	0.0% - 0.0%	0.6% - 0.7%

A summary of the Company’s PRSU activity and related information for the six months ended June 30, 2015 is presented below:



(shares and aggregate intrinsic value in millions)
	Number of Shares		Weighted- Average Grant Date Fair Value		Aggregate Intrinsic Value
Awards outstanding at December 31, 2014	0.28		$	53.45
Granted	0.26		57.52
Vested	—		—
Forfeited	(0.05	)	56.85
Awards outstanding at June 30, 2015	0.49		$	54.36	$	32.4

The maximum number of shares to be awarded under the PRSUs granted during the six months ended June 30, 2015 will be 0.78 million, which will vest, if earned at the end of the three-year performance period ending on December 31, 2017.

During the six months ended June 30, 2015, there was no common stock issued from treasury stock as a result of PRSUs being earned.

A summary of the Company’s stock option activity and related information for the six months ended June 30, 2015 is presented below:



(shares and aggregate intrinsic value in millions)
	Number of Shares		Weighted- Average Grant Date Fair Value		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Options outstanding December 31, 2014	2.84		$	24.18
Granted	0.44		57.60
Exercised	(0.88	)	11.99
Forfeited	(0.08	)	57.20
Options outstanding at June 30, 2015	2.32		$	33.85	5.84	$	71.1
Options exercisable at June 30, 2015	1.82		$	27.72	4.86	$	69.4

The aggregate intrinsic value of options exercised during the three and six months ended June 30, 2015 was $41.5 million, and $40.5 million, respectively.

A summary of the Company’s RSU and DSU activity and related information for the six months ended June 30, 2015 is presented below:



(shares and aggregate intrinsic value in millions)
	Number of Shares		Weighted- Average Grant Date Fair Value		Aggregate Intrinsic Value
Awards outstanding at December 31, 2014	0.11		$	50.41
Granted	0.00		58.98
Vested	(0.06	)	49.27
Forfeited	0.00		49.63
Awards outstanding at June 30, 2015	0.05		$	52.11	$	3.5

RSUs granted during the six months ended June 30, 2015 will vest over three years. DSUs granted during the six months ended June 30, 2015 will vest over one year.

The aggregate intrinsic value of common stock underlying RSUs issued from treasury stock during the three and six months ended June 30, 2015 was $0.6 million, and $3.7 million, respectively.

A summary of total unrecognized stock-based compensation expense based on current performance estimates related to the PRSUs, options, RSUs and DSUs granted during the six months ended June 30, 2015 is presented below:



($ in millions)
	June 30, 2015		Weighted Average Remaining Vesting Period (Years)
Unrecognized stock option expense	$	5.0	2.57 years
Unrecognized RSU/DSU expense	0.7		1.22 years
Unrecognized PRSU expense	11.0		2.50 years
Total unrecognized stock-based compensation expense	$	16.7	2.47 years