Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accounting Policies [Abstract]
Net income attributable to common stockholders (Dilutive)	$ 12,006	$ 22,162	$ 22,323	$ 23,980
Stock options, SARs and restricted stock	158	428	348	411
Earnings Per Share, On Incremental Common Shares Attributable to Share-based Payment Arrangements	$ (0.02)	$ (0.07)	$ (0.06)	$ (0.08)
Weighted Average Number of Shares Outstanding, Diluted	10,614	11,438	10,808	11,385
Diluted earnings per common share	$ 1.13000	$ 1.94000	$ 2.07000	$ 2.11000
Earnings Per Share, Basic [Abstract]
Net Income (Loss) Available to Common Stockholders, Basic	$ 12,006	$ 22,162	$ 22,323	$ 23,980
Weighted Average Number of Shares Outstanding, Basic	10,456	11,010	10,460	10,974
Basic earnings per common share	$ 1.15	$ 2.01	$ 2.13	$ 2.19