Accounting Policies - Earnings Per Share Anti-Dilutive (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic	$ 16,364	$ 8,359	$ 38,687	$ 32,339
Net Income (Loss) Available to Common Stockholders, Diluted	$ 16,364	$ 8,359	$ 38,687	$ 32,339
Stock options, SARs and restricted stock	176,000	243,000	291,000	355,000
Weighted Average Number of Shares Outstanding, Basic	10,473,000	11,028,000	10,464,000	10,992,000
Basic earnings per common share	$ 1.56	$ 0.76	$ 3.70	$ 2.94
Earnings Per Share, On Incremental Common Shares Attributable to Share-based Payment Arrangements	$ (0.02)	$ (0.02)	$ (0.10)	$ (0.09)
Weighted Average Number of Shares Outstanding, Diluted	10,649,000	11,271,000	10,755,000	11,347,000
Diluted earnings per common share	$ 1.54000	$ 0.74000	$ 3.6000	$ 2.85000
Stock Options and SARs [Members]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (shares)	54,709	476,699	115,875	302,598
Performance Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (shares)	37,284	45,034	37,284	40,194