Consolidated Statements Of Stockholders' Equity - USD ($)	Total		Common Stock	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Loss
BEGINING BALANCE (in shares) at Dec. 31, 2012			28,626,323
BEGINING BALANCE at Dec. 31, 2012	$ 549,088,000		$ 504,881,000	$ (293,149,000)	$ 338,979,000	$ (1,623,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from exercise of stock options, net (in shares)			411,902
Proceeds from exercise of stock options, net	12,655,000		$ 12,655,000
Adjustments related to tax withholding for share-based compensation (in shares)			(76,401)
Adjustments related to tax withholding for share-based compensation	(4,195,000)		$ (4,195,000)
Share-based payments expense (in shares)			223,173
Share-based payments expense	16,831,000		$ 16,831,000
Excess tax benefit on share-based compensation expense	$ 3,287,000		$ 3,287,000
Repurchases of common stock (in shares)	(3,306,433)		(3,306,433)
Repurchases of common stock	$ (195,004,000)			(195,004,000)
Conversion of callable convertible debt, net of tax (in shares)			272,336
Conversion of callable convertible debt, net of tax	(38,175,000)		$ (49,532,000)	11,357,000
Debt conversion feature (in shares)			0
Debt conversion feature	(1,446,000)		$ (1,446,000)
Net income	174,792,000				174,792,000
Foreign currency translation adjustment	856,000	[1],[2]				856,000	[3]
ENDING BALANCE (in shares) at Dec. 31, 2013			26,150,900
ENDING BALANCE at Dec. 31, 2013	518,689,000		$ 482,481,000	(476,796,000)	513,771,000	(767,000)
Statement of Stockholders' Equity (Footnote) [Abstract]
Foreign currency translation adjustment, tax effect	0
BEGINING BALANCE (in shares) at Dec. 31, 2012			28,626,323
BEGINING BALANCE at Dec. 31, 2012	$ 549,088,000		$ 504,881,000	(293,149,000)	338,979,000	(1,623,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchases of common stock (in shares)	(13,745,799)
Repurchases of common stock	$ (896,175,000)
ENDING BALANCE (in shares) at Dec. 31, 2015	16,607,516
ENDING BALANCE at Dec. 31, 2015	$ (22,074,000)		$ 485,163,000	(1,151,063,000)	643,452,000	374,000
BEGINING BALANCE (in shares) at Dec. 31, 2013			26,150,900
BEGINING BALANCE at Dec. 31, 2013	518,689,000		$ 482,481,000	(476,796,000)	513,771,000	(767,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from exercise of stock options, net (in shares)			103,260
Proceeds from exercise of stock options, net	3,735,000		$ 3,735,000
Adjustments related to tax withholding for share-based compensation (in shares)			(61,543)
Adjustments related to tax withholding for share-based compensation	(4,255,000)		$ (4,255,000)
Share-based payments expense (in shares)			227,092
Share-based payments expense	14,424,000		$ 13,036,000	1,388,000
Excess tax benefit on share-based compensation expense	$ 1,920,000		$ 1,920,000
Repurchases of common stock (in shares)	(7,925,227)		(7,925,227)
Repurchases of common stock	$ (545,140,000)			(545,140,000)
Conversion of callable convertible debt, net of tax (in shares)			431,760
Conversion of callable convertible debt, net of tax	(516,000)		$ (24,771,000)	24,255,000
Adjustment and settlement of debt conversion feature classified as temporary equity	1,446,000		$ 1,446,000
Net income	106,618,000				106,618,000
Foreign currency translation adjustment	$ 457,000	[2],[4]				457,000	[3]
ENDING BALANCE (in shares) at Dec. 31, 2014	18,926,242		18,926,242
ENDING BALANCE at Dec. 31, 2014	$ 97,378,000		$ 473,592,000	(996,293,000)	620,389,000	(310,000)
Statement of Stockholders' Equity (Footnote) [Abstract]
Foreign currency translation adjustment, tax effect	$ 0
Proceeds from exercise of stock options, net (in shares)	49,000		48,992
Proceeds from exercise of stock options, net	$ 2,552,000		$ 2,552,000
Adjustments related to tax withholding for share-based compensation (in shares)			(60,255)
Adjustments related to tax withholding for share-based compensation	(4,013,000)		$ (4,013,000)
Share-based payments expense (in shares)			206,676
Share-based payments expense	17,288,000		$ 12,258,000	5,030,000
Excess tax benefit on share-based compensation expense	$ 774,000		$ 774,000
Repurchases of common stock (in shares)	(2,514,139)		(2,514,139)
Repurchases of common stock	$ (159,800,000)			(159,800,000)
Net income	44,337,000				44,337,000
Dividends (Note 20)	(21,274,000)				(21,274,000)
Foreign currency translation adjustment	$ 684,000	[2],[5]				684,000
ENDING BALANCE (in shares) at Dec. 31, 2015	16,607,516
ENDING BALANCE at Dec. 31, 2015	$ (22,074,000)		$ 485,163,000	$ (1,151,063,000)	$ 643,452,000	$ 374,000
Statement of Stockholders' Equity (Footnote) [Abstract]
Foreign currency translation adjustment, tax effect	$ 0

[1] Foreign currency translation adjustment had no tax effect in 2013.

[2] Foreign currency translation adjustment had no tax effect in 2015, 2014 and 2013.

[3] Foreign currency translation adjustment had no tax effect for the years ended December 31, 2015, 2014 and 2013.

[4] Foreign currency translation adjustment had no tax effect in 2014.

[5] Foreign currency translation adjustment had no tax effect in 2015.