Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share (Details) [Abstract]
Number of anti-dilutive stock awards	691,491	1,297,560	1,059,078	577,742
Earnings Per Share (Table Details) [Abstract]
Net earnings	$ 39,910	$ 31,224	$ 136,033	$ 115,342
Basic weighted average shares	58,882,000	60,030,000	59,098,000	61,944,000
Effect of dilutive stock options	430,000	474,000	511,000	704,000
Diluted weighted average shares	59,312,000	60,504,000	59,609,000	62,648,000
Basic earnings per common share	$ 0.68	$ 0.52	$ 2.30	$ 1.86
Diluted earnings per common share	$ 0.67	$ 0.52	$ 2.28	$ 1.84