Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Accounting Policies [Abstract]
Net income attributable to common stockholders (Dilutive)		$ 18,615	$ 10,317
Stock options, SARs and restricted stock	[1]	231	538
Earnings Per Share, On Incremental Common Shares Attributable to Share-based Payment Arrangements	[1]	$ (0.03)	$ (0.05)
Weighted Average Number of Shares Outstanding, Diluted		10,782	11,003
Diluted earnings per common share		$ 1.73000	$ 0.94000
Earnings Per Share, Basic [Abstract]
Net Income (Loss) Available to Common Stockholders, Basic		$ 18,615	$ 10,317
Weighted Average Number of Shares Outstanding, Basic		10,551	10,465
Basic earnings per common share		$ 1.76	$ 0.99

[1] For the three months ended March 31, 2017 and 2016, stock options and SARs of 50,757 and 201,401, respectively, were outstanding but not included in the computation of diluted earnings per share of common stock because they were anti-dilutive. For the three months ended March 31, 2017 and 2016, contingent shares of non-vested restricted stock of 32,892, and 37,284, respectively, were outstanding but not included in the computation of diluted earnings per share of common stock because performance conditions had not yet been met.