Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share (Details) [Abstract]
Number of anti-dilutive stock awards	1,119,530	1,159,842	1,268,665	1,158,078
Earnings Per Share (Table Details) [Abstract]
Net earnings	$ 42,004	$ 44,182	$ 88,461	$ 96,123
Basic weighted average shares	54,885,000	59,160,000	56,416,000	59,206,000
Effect of dilutive stock options	368,000	418,000	378,000	551,000
Diluted weighted average shares	55,253,000	59,578,000	56,794,000	59,757,000
Basic earnings per common share	$ 0.77	$ 0.75	$ 1.57	$ 1.62
Diluted earnings per common share	$ 0.76	$ 0.74	$ 1.56	$ 1.61