Stock-Based Compensation

During the three- and nine-month periods ended September 30, 2015 and 2014, the Company recognized the following stock-based compensation expense in sales, general and administrative expense:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Stock-based compensation expense	$	2.7	$	1.8	$	28.1	$	5.6

The Company did not realize any excess tax benefit for tax deductions from the stock-based compensation plan in the three- and nine-month periods ended September 30, 2015 and 2014.

As discussed further in Note 3—Acquisitions, the Company settled the outstanding warrants and certain performance stock awards of ND. The portion of the fair value of the warrants and performance shares not attributable to service performed prior to the acquisition date was recorded as stock-based compensation expense in the post-combination period. The amount of stock-based compensation expense related to the settlement of ND stock awards included in the nine-month period ended September 30, 2015 was $18.5 million. The $8.5 million of stock-based compensation expense related to the warrants was settled in cash during the second quarter of 2015 in conjunction with the acquisition.

Stock Options

A summary of stock option award activity for the nine-month period ended September 30, 2015 is presented below:



	Stock Options
			Weighted Average Exercise Price			Weighted Average Grant Date Fair Value		Weighted Average Remaining Term
	Stock				Exercise
	Options				Price Range
Outstanding at December 31, 2014	1,344,795		$	11.70	$2.68 - $27.87	$	6.04	6.84
Granted	—		—		N/A	—
Exercised	(52,683	)	9.22		$2.68 - $27.87	3.55
Forfeited	(36,300	)	20.11		$12.10 - $27.87	9.56
Outstanding at September 30, 2015	1,255,812		$	11.57	$2.68 - $27.87	$	5.57	6.20
Options exercisable at September 30, 2015	1,005,812		$	11.09	$2.68 - $27.87	$	5.29	6.09

The stock-based compensation expense for stock options was $0.3 million and $0.5 million for the three-month periods ended September 30, 2015 and 2014, respectively, and $1.6 million and $1.3 million for the nine-month periods ended September 30, 2015 and 2014, respectively. As of September 30, 2015, the Company had 1,005,812 options vested and exercisable and $2.3 million of unrecognized compensation cost related to stock options. The intrinsic value of options vested and exercisable at September 30, 2015 was $12.8 million. The remaining estimated compensation expense related to the existing stock options for the periods ended December 31, 2015, 2016, 2017, 2018 and 2019 is as follows:



	2015		2016		2017		2018		2019
Remaining estimated compensation expense related to existing stock options	$	0.3	$	1.1	$	0.5	$	0.3	$	0.1

The total intrinsic value of options exercised during the nine-month periods ended September 30, 2015 and 2014 was $1.9 million and $1.7 million, respectively.

Restricted Stock Units and Performance-based Restricted Stock Units

A summary of restricted stock units (“RSU”) and performance-based restricted stock units (“PRSU”) award activity for the nine-month period ended September 30, 2015 is presented below:



	Restricted Stock Units				Performance-based Restricted Stock Units
			Weighted Average Grant Date Fair Value		Performance-based Restricted Stock Units		Weighted Average Grant Date Fair Value
	Restricted
	Stock Units
Outstanding at December 31, 2014	692,823		$	15.23	1,563,951		$	20.86
Granted	35,413		39.42		291,770		29.32
Vested	(219,587	)	14.88		(79	)	27.61
Forfeited	(32,093	)	29.03		(3,418	)	28.47
Outstanding at September 30, 2015	476,556		$	16.31	1,852,224		$	22.19

The stock-based compensation expense for outstanding RSUs was $0.8 million and $1.3 million for the three-month periods ended September 30, 2015 and 2014, respectively, and $3.0 million and $4.3 million for the nine-month periods ended September 30, 2015 and 2014, respectively. The total fair value of RSUs vested during the nine-month periods ended September 30, 2015 and 2014 was $7.9 million and $7.0 million, respectively. Of the 476,556 outstanding RSUs, 235,842 vest subject to service conditions and 240,714 vest subject to service and market conditions.

The stock-based compensation expense for outstanding PRSUs was $1.6 million and $5.0 million for the three- and nine-month periods ended September 30, 2015, respectively. No PRSUs vested during and no stock-based compensation expense was recognized for outstanding PRSUs for the nine-month period ended September 30, 2014. Of the 1,852,224 outstanding PRSUs, 1,741,643 vest subject to service and a combination of market and performance conditions and 110,581 vest subject to service and performance conditions.

As of September 30, 2015, the Company had approximately $13.2 million of unrecognized compensation cost related to non-vested RSU and PRSU compensation that is anticipated to be recognized over a weighted-average period of approximately 1.54 years. Remaining estimated compensation expense related to outstanding RSUs and PRSUs for the years ending December 31, 2015, 2016, 2017, 2018, 2019, and 2020 and thereafter is as follows:



	2015		2016		2017		2018		2019		2020 & thereafter
Remaining estimated compensation expense related to outstanding RSUs and PRSUs deemed probable	$	3.1	$	5.0	$	2.1	$	1.2	$	0.3	$	1.5

The remaining estimated compensation expense excludes the impact of PRSUs not deemed probable as of September 30, 2015. The unrecognized compensation cost related to PRSUs not deemed probable as of September 30, 2015 is $20.0 million.