Significant Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share Reconciliation
Net earnings (loss)	$ (3,204,640)	$ (3,096)	$ (24,673)	$ 25,189	$ 209,730	$ 125,357	$ 106,049	$ 101,715	$ (3,207,220)	$ 542,851	$ 237,838
Weighted average common shares outstanding - basic									153,192,000	153,136,000	152,963,000
Effect of dilutive instruments									0	1,558,000	1,463,000
Weighted average common shares outstanding - fully diluted									153,192,000	154,694,000	154,426,000
Net (income (loss) per common share - basic	$ (20.91)	$ (0.02)	$ (0.16)	$ 0.16	$ 1.37	$ 0.82	$ 0.69	$ 0.66	$ (20.94)	$ 3.54	$ 1.55
Net income (loss) per common share - fully diluted	$ (20.91)	$ (0.02)	$ (0.16)	$ 0.16	$ 1.36	$ 0.81	$ 0.68	$ 0.66	$ (20.94)	$ 3.51	$ 1.54
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount									1,700,000	1,377,000	1,406,000