Capital Stock (Details) (USD $)	0 Months Ended	12 Months Ended				0 Months Ended						12 Months Ended	13 Months Ended	0 Months Ended		12 Months Ended
	Aug. 07, 2006	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Feb. 25, 2013	Aug. 07, 2006 Benefical Owner of Common Stock Percentage [Member]	Aug. 07, 2006 Percentage of Common Stock Owned [Member]	Aug. 07, 2006 Percentage of Rights Owned By Individual Beneficial Owner Not Deemed Acquiring Person [Member]	Aug. 07, 2006 Percentage of Assets Sold [Member]	Aug. 07, 2006 Beneficial Owner of a Percentage of Outstanding Common Stock [Member]	Mar. 18, 2010 2010 Stock Repurchase Program [Member]	Dec. 31, 2011 2010 Stock Repurchase Program [Member]	Apr. 30, 2011 2010 Stock Repurchase Program [Member]	Mar. 08, 2012 2011 Stock Repurchase Program [Member]	May 02, 2011 2011 Stock Repurchase Program [Member]	Dec. 31, 2012 2011 Stock Repurchase Program [Member]	Dec. 31, 2011 2011 Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock, shares issued		148,727,000	146,804,000
Treasury stock, shares		67,426,000	64,847,000		70,645,233
Common stock, outstanding		81,301,000
Purchase rate of rights	0.001
Preferred stock, par value	$ 0.001	$ 0.001	$ 0.001
Purchase price, per right	170
Terms of rights agreement						15.00%	10.00%	20.00%	50.00%	50.00%
Period rights separated from common stock	10 days
Period following the commencement of a tender or exchange offer	10 days
Period following determination an individual has become a beneficial owner	10 days
Beneficial owner of common stock, percentage						15.00%
Price per redeemable right	0.01
Stock repurchase program authorized amount											$ 300,000,000		$ 300,000,000	$ 323,700,000	$ 300,000,000
Treasury stock shares acquired												4,900,000	10,800,000			2,100,000	8,700,000
Treasury stock value acquired cost method		69,496,000	396,273,000	237,134,000								149,800,000	300,000,000			50,000,000	223,700,000
Average price of repurchased stock per share													$ 27.80
Stock repurchase program remaining authorized repurchase amount																$ 350,000,000	$ 76,300,000