Reconciliation of Earnings Per Share (Reconciliation) (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
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income (Loss)	$ (590,806)	$ (227,904)	$ (111,601)	$ (15,420)	$ 65,418	$ 457,251	$ (7,953)	$ 53,316	$ (945,731)	$ 568,032	$ 204,554
Basic Shares Outstanding (in shares)									76,078,371	72,896,579	72,317,865
Basic earnings per average common share (in dollars per share)	$ (7.50)	$ (2.89)	$ (1.52)	$ (0.21)	$ 0.90	$ 6.26	$ (0.11)	$ 0.73	$ (12.43)	$ 7.79	$ 2.83
Effect of dilutive securities
Net Income (Loss), Diluted EPS	$ (590,806)	$ (227,904)	$ (111,601)	$ (15,420)	$ 65,418	$ 457,251	$ (7,953)	$ 53,316	$ (945,731)	$ 568,032	$ 204,554
Diluted Shares Outstanding (in shares)									76,078,371	73,274,631	72,470,622
Diluted earnings per average common share (in dollars per share)	$ (7.50)	$ (2.89)	$ (1.52)	$ (0.21)	$ 0.89	$ 6.22	$ (0.11)	$ 0.73	$ (12.43)	$ 7.75	$ 2.82
Stock options
Effect of dilutive securities
Effect of dilutive securities									0	216,000	112,000
Non-vested restricted stock
Effect of dilutive securities
Effect of dilutive securities									0	58,000	20,000
Performance share awards
Effect of dilutive securities
Effect of dilutive securities									0	104,000	21,000