Share Repurchase Programs (Details) (USD $)	12 Months Ended						12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 December Two Thousand Eleven Anti Dilutive Share Repurchase Program [Member] [Member]	Dec. 31, 2010 February 2010 Discretionary Share Repurchase Program [Member]	Feb. 28, 2010 February 2010 Discretionary Share Repurchase Program [Member]	Dec. 31, 2011 December 2009 Anti-Dilutive Share Repurchase Program [Member]	Dec. 31, 2010 December 2009 Anti-Dilutive Share Repurchase Program [Member]	Dec. 31, 2012 December 2009 Anti-Dilutive Share Repurchase Program [Member]	Dec. 31, 2012 Common Stock [Member]	Dec. 31, 2011 Common Stock [Member]	Dec. 31, 2010 Common Stock [Member]
Share Repurchase Programs (Textual) [Abstract]
Discretionary Share Repurchase Program Authorization						$ 100,000,000
Maximum period of discretionary share repurchase program						2 years
Repurchased and retired shares					2,420,390			561,656		543,923	1,175,783	2,982,046
Aggregate cost of repurchased and retired	$ 26,343,000	$ 59,102,000	$ 123,170,000	$ 26,000,000	$ 100,000,000		$ 59,000,000	$ 23,000,000		$ 272,000	$ 588,000	$ 1,491,000
Maximum number of share repurchases authorization				2,000,000					2,000,000