Stockholders' Equity And Share-Based Awards (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended										1 Months Ended				12 Months Ended
	Jan. 26, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Restricted Shares [Member]	Dec. 31, 2010 Restricted Shares [Member]	Dec. 31, 2009 Restricted Shares [Member]	Dec. 31, 2011 Restricted Stock With Common Stock Price Thresholds [Member]	Dec. 31, 2010 Restricted Stock With Common Stock Price Thresholds [Member]	Dec. 31, 2009 Restricted Stock With Common Stock Price Thresholds [Member]	Dec. 31, 2011 Performance Based Restricted Share Awards [Member]	Aug. 31, 2011 New Stock Repurchase Program [Member]	Aug. 31, 2011 Prior Stock Repurchase Program [Member]	Jan. 31, 2011 Annual Grant [Member] Executive Officer [Member] Restricted Shares [Member]	Jan. 31, 2010 One Time Grant [Member] Executive Officer [Member] Restricted Shares [Member]	Dec. 31, 2011 Minimum [Member]	Dec. 31, 2010 Minimum [Member]	Dec. 31, 2009 Minimum [Member]	Dec. 31, 2011 Maximum [Member]	Dec. 31, 2010 Maximum [Member]	Dec. 31, 2009 Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based awards collectively available for grant		2,400,000
Share-based award explicit service period, (in years)																3	3	3	4	4	4
Contractual life of share-based payment plans, (in years)		7	7	7											5
Weighted average per share grant date fair value of grants during the year			$ 16.89	$ 9.91	$ 28.55	$ 31.00	$ 24.08	$ 29.50	$ 30.72	$ 10.99
Restricted share awards granted					1,246,800						800,000			400,000	1,400,000
Aggregate grant date fair value of share-based awards											$ 24.3			$ 11.7	$ 44.8
Unrecognized compensation cost related to non-vested share-based awards		31.5
Weighted average period to recognize compensation costs (months)		14
Stock repurchase program, authorized amount	500											500	150
Shares repurchased under stock repurchase program		2,500,000	1,400,000
Weighted average price of shares repurchased		$ 30.42	$ 29.62
Cash dividends paid to stockholders		30.1	28.7	6.6
Shares issued in equity offering				12,000,000
Price per share received in equity offering				$ 17.50
Proceeds from issuance of common stock, net				$ 202.7
Warrants outstanding, number of shares to purchase		2,200,000
Exercise price of warrants		$ 45.32
Threshold price for mandatory exercise price of warrants		$ 50.99
Threshold price for mandatory exercises of warrants if notes are redeemed		$ 45.32