Share Repurchase Programs (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended	3 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012 December 2011 Anti-Dilutive Share Repurchase Program [Member]	Jun. 30, 2012 December 2011 Anti-Dilutive Share Repurchase Program [Member]	Jun. 30, 2011 December 2011 Anti-Dilutive Share Repurchase Program [Member]	Dec. 31, 2011 December 2011 Anti-Dilutive Share Repurchase Program [Member]	Jun. 30, 2012 December 2009 Anti-Dilutive Share Repurchase Program [Member]	Jun. 30, 2011 December 2009 Anti-Dilutive Share Repurchase Program [Member]	Dec. 31, 2009 December 2009 Anti-Dilutive Share Repurchase Program [Member]
Share Repurchase Programs (Textuals) [Abstract]
Maximum number of share repurchases authorization					2,000,000			2,000,000
Repurchased and retired shares		233,500	456,700	820,000		570,000
Aggregate cost of repurchased and retired	$ 22,867	$ 10,900	$ 22,900			$ 29,900	$ 41,900
Maximum period of discretionary share repurchase program								2 years