Accounting Policies - Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Earnings Per Share, Basic [Abstract]
Net income attributable to common stockholders	$ 15,413		$ 16,381		$ 59,348		$ 34,293
Weighted Average Number of Shares Outstanding, Basic	10,843		10,492		10,799		10,442
Basic earnings per common share (dollars per share)	$ 1.42		$ 1.56		$ 5.50		$ 3.28
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Weighted-average shares, dilutive securities, stock options, SARs, and restricted stock (shares)	370	[1]	504	[1]	392	[2]	532	[2]
Earnings Per Share, On Incremental Common Shares Attributable to Share-based Payment Arrangements	$ (0.05)	[1]	$ (0.07)	[1]	$ (0.20)	[2]	$ (0.16)	[2]
Net Income (Loss) Available to Common Stockholders, Diluted	$ 15,413		$ 16,381		$ 59,348		$ 34,293
Weighted-average shares, diluted (shares)	11,213		10,996		11,191		10,974
Diluted Earnings per common share	$ 1.37		$ 1.49		$ 5.30		$ 3.12

[1] For the three months ended September 30, 2013 and 2012, stock options and SARs of 36,983 and 296,873, 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 September 30, 2013 and 2012, contingent shares of non-vested restricted stock of 44,894 and 106,300, 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 nine months ended September 30, 2013 and 2012, stock options and SARs of 43,640 and 412,009, respectively, were outstanding but not included in the computation of diluted earnings per share of common stock because they were anti-dilutive. For the nine months ended September 30, 2013 and 2012, contingent shares of non-vested restricted stock of 38,363 and 97,300, respectively, were outstanding but not included in the computation of diluted earnings per share of common stock because performance conditions were not met.