Consolidated Statements Of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified		Total		Common Stock [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
BALANCE at Dec. 31, 2012		$ 549,088		$ 504,881	$ (293,149)	$ 338,979	$ (1,623)
BALANCE (in shares) at Dec. 31, 2012		28,626,323		28,626,323
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from exercise of stock options, net (in shares)				381,773
Proceeds from exercise of stock options, net		11,775		11,775
Adjustments related to tax withholding for share-based compensation (in shares)				(73,591)
Adjustments related to tax withholding for share-based compensation		(4,012)		(4,012)
Share-based payments expense (in shares)				295,330
Share-based payments expense		11,454		11,454
Tax benefit on share-based compensation expense		2,925		2,925
Repurchases of common stock (in shares)				(1,792,742)
Repurchases of common stock		(95,004)			(95,004)
Repurchase and conversion of callable convertible debt, net of tax (in shares)		255,745		255,745
Repurchase and conversion of callable convertible debt, net of tax		(38,896)		(49,539)	10,643
Reclassification of debt conversion feature to temporary equity		(2,080)		(2,080)
Net income		152,117				152,117
Foreign currency translation adjustment	[1]	(304)	[2]				(304)
BALANCE at Sep. 30, 2013		587,063		475,404	(377,510)	491,096	(1,927)
BALANCE (in shares) at Sep. 30, 2013		27,692,838		27,692,838
BALANCE at Jun. 30, 2013		521,563		470,777	(353,875)	408,440	(3,779)
BALANCE (in shares) at Jun. 30, 2013				28,060,007
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from exercise of stock options, net (in shares)				37,767
Proceeds from exercise of stock options, net		1,256		1,256
Adjustments related to tax withholding for share-based compensation (in shares)				(4,850)
Adjustments related to tax withholding for share-based compensation		330		330
Share-based payments expense (in shares)				7,464
Share-based payments expense		2,774		2,774
Tax benefit on share-based compensation expense		293		293
Repurchases of common stock (in shares)				(407,796)
Repurchases of common stock		(23,616)			(23,616)
Repurchase and conversion of callable convertible debt, net of tax (in shares)				246
Repurchase and conversion of callable convertible debt, net of tax		(45)		(26)	(19)
Net income		82,656				82,656
Foreign currency translation adjustment	[1]	1,852	[2]				1,852
BALANCE at Sep. 30, 2013		$ 587,063		$ 475,404	$ (377,510)	$ 491,096	$ (1,927)
BALANCE (in shares) at Sep. 30, 2013		27,692,838		27,692,838

[1] Foreign currency translation adjustment has no tax effect for the nine months ended September 30, 2013.

[2] Foreign currency translation adjustment has no tax effect for the three and nine months ended September 30, 2013 and 2012, respectively.