Accounting Policies - Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended							12 Months Ended						15 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Sep. 30, 2012
Earnings Per Share, Basic [Abstract]
Net income attributable to common stockholders	$ 9,601	$ 16,381	$ (4,291)	$ 22,203	$ 13,323	$ 5,170	$ 18,323	$ 43,894		$ 13,784		$ 22,080		$ (23,032)
Weighted-average shares, basic (shares)								10,479		10,335		10,229
Basic earnings per common share (dollars per share)	$ 0.91	$ 1.56	$ (0.41)	$ 2.14	$ 1.29	$ 0.50	$ 1.78	$ 4.19		$ 1.33		$ 2.16		$ (2.22)
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Weighted-average shares, dilutive securities, stock options, SARs, and restricted stock (shares)								540	[1]	467	[1]	386	[1]
Earnings Per Share, dilutive securities, stock options, SARs, and restricted stock (dollars per share)								$ (0.21)	[1]	$ (0.05)	[1]	$ (0.08)	[1]
Net (loss)/Income income attributable to common stockholders, diluted								$ 43,894		$ 13,784		$ 22,080
Weighted-average shares, diluted (shares)								11,019		10,802		10,615
Diluted Earnings per common share	$ 0.87	$ 1.49	$ (0.41)	$ 2.04	$ 1.23	$ 0.48	$ 1.72	$ 3.98		$ 1.28		$ 2.08		$ (2.22)

[1] )For the years ended December 31, 2012, 2011, and 2010, stock options and SARs of 317,253, 703,624, and 1,485,404, respectively, were outstanding but not included in the computation of diluted earnings per share of common stock because they were anti-dilutive. For the years ended December 31, 2012, 2011, and 2010, contingent shares of non-vested restricted stock of 79,300, 76,340, and 115,125, respectively, were outstanding but not included in the computation of diluted earnings per share of common stock because performance conditions were not me