Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Net earnings	$ 25,306	$ 27,165	$ 71,696	$ 115,174
Basic weighted average shares	52,864,000	53,438,000	52,828,000	55,423,000
Basic earnings per common share	$ 0.48	$ 0.51	$ 1.36	$ 2.08
Net earnings, diluted	$ 25,306	$ 27,165	$ 71,696	$ 115,174
Effect of dilutive stock options	250,000	374,000	241,000	377,000
Diluted weighted average shares	53,114,000	53,812,000	53,069,000	55,800,000
Diluted earnings per common share	$ 0.48	$ 0.50	$ 1.35	$ 2.06
Earnings Per Share (Details) [Abstract]
Number of anti-dilutive stock awards	2,507,547	1,183,826	2,513,948	1,340,372