Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net earnings	$ (866,628)	$ 96,422	$ 128,757
Basic weighted average shares	53,050,000	52,850,000	54,804,000
Effect of dilutive stock options	0	276,000	358,000
Diluted weighted average shares	53,050,000	53,126,000	55,162,000
Basic earnings per common share	$ (16.34)	$ 1.82	$ 2.35
Diluted earnings per common share	$ (16.34)	$ 1.81	$ 2.33
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive stock options	2,585,711	2,496,147	1,507,355