Net Income per Share (Tables)

6 Months Ended

Jun. 30, 2013

Earnings Per Share [Abstract]

Schedule of calculation of numerator and denominator in earnings per share

	Three Months Ended				Six Months Ended
	June 30,				June 30,
Net Income per Basic and Diluted Share:	2013		2012		2013		2012
(in thousands except per share amounts)
Numerator
Net income used to compute net income per basic share	$	93,742	$	73,502	$	147,213	$	113,686
Add back interest expense for convertible notes, net of estimated tax of approximately $3 for each of the three months ended June 30, 2013 and 2012, and $7 and $18 for the six months ended June 30, 2013 and 2012, respectively (see Note 9)	6		6		13		33
Net income used to compute net income per diluted share	$	93,748	$	73,508	$	147,226	$	113,719
Denominator
Total weighted-average shares used to compute net income per basic share	139,825		139,683		139,821		139,681
Restricted stock outstanding	75		100		71		84
Effect of dilutive stock options	19		15		19		15
Assumed conversion of Series 2012 Notes	8,304		2,252		8,693		2,189
Assumed conversion of May 2015 Notes	3,825		—		4,004		—
Assumed conversion of February 2015 Notes	176		163		176		921
Weighted-average shares used to compute net income per diluted share	152,224		142,213		152,784		142,890
Net income per basic share	$	0.67	$	0.53	$	1.05	$	0.81
Net income per diluted share	$	0.62	$	0.52	$	0.96	$	0.80