Statements of Changes in Stockholders' Equity (USD $) In Millions	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2010	$ 1,820.5	$ 1.4	$ (26.8)	$ 1,449.7	$ 421.0	$ (24.8)
Beginning balance (in shares) at Dec. 31, 2010		139.0	(1.4)
Comprehensive income	172.8				204.7	(31.9)
Restricted stock awards, stock options exercised and stock plan purchases (in shares)			3.5
Restricted stock awards, stock options exercised and stock plan purchases	21.9		75.1	(53.2)
Restricted stock awards cancelled and shares tendered for stock options and taxes (in shares)			(1.0)
Restricted stock awards cancelled and shares tendered for stock options and taxes	(19.6)		(23.4)	3.8
Dividends declared	(31.3)				(31.3)
Stock-based compensation	23.8			23.8
Shares repurchased (in shares)			(3.8)
Shares repurchased	(76.1)		(76.1)
Ending balance at Dec. 31, 2011	1,912.0	1.4	(51.2)	1,424.1	594.4	(56.7)
Ending balance (in shares) at Dec. 31, 2011		139.0	(2.7)
Comprehensive income	247.2				243.9	3.3
Restricted stock awards, stock options exercised and stock plan purchases (in shares)			3.6
Restricted stock awards, stock options exercised and stock plan purchases	68.2		74.7	(6.5)
Restricted stock awards cancelled and shares tendered for stock options and taxes (in shares)			(1.1)
Restricted stock awards cancelled and shares tendered for stock options and taxes	(28.0)		(29.7)	1.7
Stock-based compensation	67.1			67.1
Shares repurchased (in shares)			(21.5)
Shares repurchased	(556.2)		(556.2)
Equity component of convertible notes, net of tax and other	49.3			49.3
Ending balance at Dec. 31, 2012	1,759.6	1.4	(562.4)	1,535.7	838.3	(53.4)
Ending balance (in shares) at Dec. 31, 2012		139.0	(21.7)
Comprehensive income	198.7				203.9	(5.2)
Proceeds from issuance of common stock, net	744.9	0.2		744.7
Proceeds from issuance of common stock, net, shares		16.5
Restricted stock awards, stock options exercised and stock plan purchases (in shares)			2.0
Restricted stock awards, stock options exercised and stock plan purchases	17.3		48.0	(30.7)
Restricted stock awards cancelled and shares tendered for stock options and taxes (in shares)			(1.3)
Restricted stock awards cancelled and shares tendered for stock options and taxes	(47.8)		(52.7)	4.9
Stock-based compensation	95.8			95.8
Shares repurchased (in shares)			(5.6)
Shares repurchased	(250.0)		(250.0)
Equity component of convertible notes, net of tax and other	31.2			31.2
Equity component of convertible notes, net of tax and other, shares		0.1
Ending balance at Dec. 31, 2013	$ 2,549.7	$ 1.6	$ (817.1)	$ 2,381.6	$ 1,042.2	$ (58.6)
Ending balance (in shares) at Dec. 31, 2013		155.6	(26.6)