Accounting Policies - Earnings Per Share Anti-Dilutive (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) Available to Common Stockholders, Basic	$ 15,032	$ 8,359	$ 22,162	$ 1,818	$ 5,647	$ 11,586	$ 20,205	$ 813	$ 47,371	$ 38,251	$ 71,833
Net Income (Loss) Available to Common Stockholders, Diluted									$ 47,371	$ 38,251	$ 71,833
Stock options, SARs and restricted stock									360,000	447,000	393,000
Weighted Average Number of Shares Outstanding, Basic									10,949,000	10,920,000	10,816,000
Basic earnings per common share	$ 1.39	$ 0.76	$ 2.01	$ 0.17	$ 0.52	$ 1.06	$ 1.85	$ 0.07	$ 4.33	$ 3.50	$ 6.64
Earnings Per Share, On Incremental Common Shares Attributable to Share-based Payment Arrangements									$ (0.14)	$ (0.13)	$ (0.23)
Weighted Average Number of Shares Outstanding, Diluted									11,309,000	11,367,000	11,209,000
Diluted earnings per common share	$ 1.35	$ 0.74	$ 1.94	$ 0.16	$ 0.50	$ 1.02	$ 1.78	$ 0.07	$ 4.19000	$ 3.37000	$ 6.41000
Stock Options and SARs [Members]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (shares)									304,132	109,143	33,730
Performance Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (shares)									46,303	36,784	26,696