Accounting Policies - Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Accounting Policies [Abstract]
Net Income (Loss) Available to Common Stockholders, Diluted	$ 20,205		$ 27,745		$ 21,018		$ 43,935
Net Income (Loss) Available to Common Stockholders, Basic	$ 20,205		$ 27,745		$ 21,018		$ 43,935
Earnings Per Share, Basic [Abstract]
Stock options, SARs and restricted stock, Weighted-Average Shares	437	[1]	383	[1]	448	[2]	403	[2]
Stock options, SARs and restricted stock (in usd per share)	$ (0.07)	[1]	$ (0.09)	[1]	$ (0.08)	[2]	$ (0.15)	[2]
Weighted Average Number of Shares Outstanding, Basic	10,924		10,815		10,906		10,776
Basic earnings per common share	$ 1.85		$ 2.57		$ 1.93		$ 4.08
Weighted Average Number of Shares Outstanding, Diluted	11,361		11,198		11,354		11,179
Diluted earnings per common share	$ 1.78		$ 2.48		$ 1.85		$ 3.93

[1] For the three months ended June 30, 2014 and 2013, stock options and SARs of 121,468 and 89,937, 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 June 30, 2014 and 2013, contingent shares of non-vested restricted stock of 42,514 and 44,894, respectively, were outstanding but not included in the computation of diluted earnings per share of common stock because performance conditions were not met.

[2] For the six months ended June 30, 2014 and 2013, stock options and SARs of 77,226 and 46,969, respectively, were outstanding but not included in the computation of diluted earnings per share of common stock because they were anti-dilutive. For the six months ended June 30, 2014 and 2013, contingent shares of non-vested restricted stock of 37,054 and 35,097, respectively, were outstanding but not included in the computation of diluted earnings per share of common stock because performance conditions were not met.