Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2014

Earnings Per Common Share

Schedule of components of basic and diluted earnings per share

The components of basic and diluted earnings per share are as follows (in thousands, except per share amounts):

	Year Ended December 31,
	2014		2013		2012
Numerator:
Net income	$	340,074	$	174,560	$	304,442
Denominator:
Weighted average outstanding shares—basic		48,176		50,076		52,093
Effect of dilutive securities(1):
Convertible notes		2,630		1,736		218
Warrants		1,910		276		—
Stock options and employee stock purchase plan		1,439		1,143		969
Weighted average shares—diluted		54,155		53,231		53,280
Earnings per common share:
Basic	$	7.06	$	3.49	$	5.84
Diluted	$	6.28	$	3.28	$	5.71
Stock options and warrants excluded from calculation(2)		9,273		11,210		11,862

(1)	Calculated using the treasury stock method.
(2)	Certain stock options and warrants have been excluded from the computation of diluted earnings per share because their impact would be anti-dilutive.

Stock Options

Stock Option Plan

Summary of assumptions to estimate the grant date fair value of stock options

Summary of assumptions to estimate the grant date fair value of stock options

	Year Ended December 31,
	2014			2013
Expected volatility		32.6	%		33.0	%
Risk-free interest rate		1.7	%		1.8	%
Expected term of options (in years)		5.0			5.0
Expected forfeiture rate		0.0	%		0.0	%
Expected dividend yield		0.0	%		0.0	%

Schedule of stock option activity

	Options			Weighted- Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value (in 000s)
Outstanding at January 1, 2014		4,749,449		$	56.06
Granted		723,869			129.49
Exercised		(1,414,369	)		34.16
Forfeited		(4,178	)		34.35
Outstanding and exercisable at December 31, 2014		4,054,771		$	76.83		6.4	$	213,505

Schedule of share-based compensation expense related to employee stock options

        Total share-based compensation expense relating to employee stock options is as follows (in thousands):

	Year Ended December 31,
	2014			2013			2012
Selling, general and administrative	$	29,460		$	36,097		$	3,024
Related income tax benefit		(10,429	)		(13,566	)		(1,115	)
Share-based compensation expense, net of taxes	$	19,031		$	22,531		$	1,909

Summary of employee and non-employee stock option exercise data

        Employee and non-employee stock option exercise data is summarized below (dollars in thousands):

	Year Ended December 31,
	2014		2013		2012
Number of options exercised		1,462,369		876,115		575,944
Cash received from options exercised	$	50,168	$	26,620	$	14,290
Total intrinsic value of options exercised	$	108,425	$	37,530	$	15,508
Tax benefits realized from options exercised	$	30,845	$	9,299	$	3,054