CONSOLIDATED 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, 2011	$ 1,912.0	$ 2.1	$ (51.2)	$ 1,423.4	$ 594.4	$ (56.7)
Beginning balance (in shares) at Dec. 31, 2011		208.6	(4.0)
Comprehensive income	247.2				243.9	3.3
Restricted stock awards, stock options exercised and stock plan purchases (in shares)			5.5
Restricted stock awards, stock options exercised and stock plan purchases	68.2		74.7	(6.5)
Restricted stock awards cancelled and shares tendered (in shares)			(1.7)
Restricted stock awards cancelled and shares tendered	(28.0)		(29.7)	1.7
Stock-based compensation	67.1			67.1
Shares repurchased (in shares)			(32.3)
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	2.1	(562.4)	1,535.0	838.3	(53.4)
Ending balance (in shares) at Dec. 31, 2012		208.6	(32.5)
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		24.7
Restricted stock awards, stock options exercised and stock plan purchases (in shares)			3.0
Restricted stock awards, stock options exercised and stock plan purchases	17.3		48.0	(30.7)
Restricted stock awards cancelled and shares tendered (in shares)			(2.0)
Restricted stock awards cancelled and shares tendered	(47.8)		(52.7)	4.9
Stock-based compensation	95.8			95.8
Shares repurchased (in shares)			(8.4)
Shares repurchased	(250.0)		(250.0)
Equity component of convertible notes, net of tax and other	31.2			31.2
Ending balance at Dec. 31, 2013	2,549.7	2.3	(817.1)	2,380.9	1,042.2	(58.6)
Ending balance (in shares) at Dec. 31, 2013		233.3	(39.9)
Comprehensive income	120.4				242.5	(122.1)
Restricted stock awards, stock options exercised and stock plan purchases (in shares)			5.9
Restricted stock awards, stock options exercised and stock plan purchases	6.7		94.7	(88.0)
Restricted stock awards cancelled and shares tendered (in shares)			(2.1)
Restricted stock awards cancelled and shares tendered	(41.8)		(82.3)	40.5
Stock-based compensation	49.7			49.7
Shares repurchased (in shares)			(5.2)
Shares repurchased	(207.8)		(207.8)
Equity component of convertible notes, net of tax and other	132.4			132.4
Ending balance at Dec. 31, 2014	$ 2,609.3	$ 2.3	$ (1,012.5)	$ 2,515.5	$ 1,284.7	$ (180.7)
Ending balance (in shares) at Dec. 31, 2014		233.3	(41.3)