Basis of Presentation (Tables)

9 Months Ended

Sep. 30, 2016

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Reconciliation of basic earnings per share ("EPS") to diluted EPS

The following is a reconciliation of basic earnings per common share to diluted earnings per share for the three months and nine months ended September 30,2016 and 2015, respectively:

	Three Months Ended   September 30,				Nine Months Ended   September 30,
(in thousands, except per share amounts)	2016		2015		2016		2015
Net income available to common stockholders	$	29,797	$	21,595	$	72,341	$	53,156
Basic weighted-average shares outstanding	48,119		48,998		48,231		49,157
Dilutive effect of potential common stock equivalents — stock options and restricted stock units	233		241		198		220
Diluted weighted-average shares outstanding	48,352		49,239		48,429		49,377
Earnings per common share:
Basic	$	0.62	$	0.44	$	1.50	$	1.08
Diluted	$	0.62	$	0.44	$	1.49	$	1.08
Potentially dilutive securities excluded from earnings per diluted share because their effect is anti-dilutive	—		—		—		—

Stock option and restricted stock unit activity of the entity

The following table represents the Company’s stock option and restricted stock unit activity for the three months and nine months ended September 30,2016 and 2015, respectively:

	Three Months Ended September 30,					Nine Months Ended September 30,
(in thousands)	2016		2015			2016		2015
Stock-based compensation expense recognized in operating expenses	$	3,141	$	2,794		$	8,995	$	8,869
Less: Tax benefit of stock-based compensation expense in provision for income taxes	1,112		1,005			3,262		3,144
Stock-based compensation expense, net of tax	$	2,029	$	1,789		$	5,733	$	5,725
Fair value of shares vested	$	3,088	$	2,749		$	9,039	$	8,744
Proceeds to the Company from the exercise of stock-based compensation	$	4,166	$	1,443		$	6,695	$	7,019
Tax effect from the exercise of stock-based compensation, including shortfall tax benefits	$	121	$	(58	)	$	140	$	(244	)

	At September 30,
(in thousands)	2016		2015
Stock-based compensation cost capitalized in inventory	$	463	$	464

Summary of financial instruments

The balances of the Company’s primary financial instruments at the dates indicated were as follows:

	At September 30,				At December 31,
(in thousands)	2016		2015		2015
United States Treasury securities and money market funds	$	13,334	$	76,488	$	76,047

Schedule of effective tax rates and income tax expense

The following table presents the Company’s effective tax rates and income tax expense for the three months and nine months ended September 30,2016 and 2015, respectively:

	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands, except percentages)	2016			2015			2016			2015
Effective tax rate	34.8		%	38.4		%	35.9		%	38.4		%
Provision for income taxes	$	15,898		$	13,479		$	40,601		$	33,115