Consolidated Statements Of Shareholders' Equity (USD $) In Millions, except Share data	Common Stock [Member]	Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at at Dec. 31, 2010	$ 0.3	$ 31.0	$ 443.3	$ (0.1)	$ 474.5
Balance, shares at at Dec. 31, 2010	27,303,946
Net income			188.0		188.0
Other comprehensive income (loss)				0.1	0.1
Stock-based compensation		1.9			1.9
Restricted stock awards, net of forfeitures, shares	(842)
Repurchase of common stock		(0.4)	(130.4)		(130.8)	[1]
Repurchase of common stock, shares	(1,979,444)				(1,979,444)
Stock options exercised		2.9			2.9
Stock options exercised, shares	300,024
Tax benefits from stock-based compensation plans		3.4			3.4
Balance at at Dec. 31, 2011	0.3	38.8	500.9		540.0
Balance, shares at at Dec. 31, 2011	25,623,684
Net income			219.7		219.7
Other comprehensive income (loss)				(0.1)	(0.1)
Stock-based compensation		12.2			12.2
Restricted stock awards, net of forfeitures, shares	195,679
Repurchase of common stock	(0.1)	(0.2)	(152.2)		(152.5)	[1]
Repurchase of common stock, shares	(1,740,372)				(1,740,372)
Stock options exercised		0.6			0.6
Stock options exercised, shares	35,905
Tax benefits from stock-based compensation plans		2.0			2.0
Balance at at Dec. 31, 2012	0.2	53.4	568.4	(0.1)	621.9	[2]
Balance, shares at at Dec. 31, 2012	24,114,896				24,114,896
Net income			253.1		253.1
Other comprehensive income (loss)				(0.1)	(0.1)
Stock-based compensation		8.5			8.5
Restricted stock awards, net of forfeitures, shares	8,349
Repurchase of common stock		(0.6)	(134.6)		(135.2)	[1]
Repurchase of common stock, shares	(1,216,015)				(1,216,015)
Restricted stock units converted to common stock	848
Stock options exercised		0.6			0.6
Stock options exercised, shares	35,000
Tax benefits from stock-based compensation plans		1.3			1.3
Balance at at Dec. 31, 2013	$ 0.2	$ 63.2	$ 686.9	$ (0.2)	$ 750.1	[2]
Balance, shares at at Dec. 31, 2013	22,943,078				22,943,078

[1] Tender Offer Cost amounts include offering costs of $0.3 million and $0.2 million for 2012 and 2011, respectively.

[2] No dividends were paid during the periods presented.