Stockholders' Equity (Narrative) (Details) (USD $)	1 Months Ended		12 Months Ended				12 Months Ended			12 Months Ended			12 Months Ended
	Sep. 30, 2007	Apr. 30, 2004	Dec. 31, 2011	Dec. 31, 2008	Dec. 31, 2010	Dec. 31, 1990	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2009 Stock Options [Member]	Dec. 31, 2011 Restricted Stock And Restricted Stock Units [Member]	Dec. 31, 2011 Stock Options And Stock Appreciation Rights [Member]	Dec. 31, 2011 1997 Directors' Plan [Member]	Dec. 31, 2011 Amended 1997 Directors' Plan [Member]
Stockholders' Equity [Line Items]
Authorized shares of preferred stock						6,000,000
Preferred stock par value						$ 0.0001
Share repurchase program, authorized amount	$ 75,000,000	$ 50,000,000
Share repurchase program, shares repurchased	1,643,000	849,000
Share repurchase program, repurchased amount	31,400,000	32,200,000
Authorized amount remaining for stock repurchases	17,800,000		43,600,000
Options, exercisable			1,398,000				1,398,000	1,765,000	2,648,000
Weighted average exercise prices of options			$ 34.75				$ 34.75	$ 32.97	$ 34.74
Exercise price ranges of outstanding options							2,286,000
Common stock reserved for future issuance			4,708,000							363,000
Maximum term of the stock options											10
Stock options, vesting period							four			four			one
Receipt of annual grant of restricted stock units by non-employee directors				100,000
Common stock reserved for issuance under plan			2,286,000		3,132,000							142
Percentage of common stock on tender offer			15.00%
Tender offer exercise price			$ 225
Redemption rights, per right			$ 0.01
Number of shares converted to in conversion			1.000
Percentage that Participating Preferred Stock is divided by after multiplying by exercise price			50.00%