Common Stock (Basic And Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Class of Stock Disclosures [Abstract]
Basic number of common shares outstanding	39,911,032	42,308,097	40,756,509	42,776,922
Dilutive effect of unvested performance awards	66,201	169,426	180,851	126,051
Dilutive effect of stock options	22,276	45,762	24,647	61,217
Diluted number of common shares outstanding	39,999,509	42,523,285	40,962,007	42,964,190
Net income	$ 3,344	$ 6,775	$ 100,108	$ 95,929
Income allocated to participating restricted stock	(24)	(28)	(440)	(391)
Net income available to common shareholders, basic	3,320	6,747	99,668	95,538
Income reallocated to participating restricted stock	(24)	(28)	(439)	(390)
Net income available to common shareholders, diluted	$ 3,320	$ 6,747	$ 99,669	$ 95,539
Earnings Per Share, Basic, Distributed	$ 0.22	$ 0.00	$ 0.88	$ 0.00
Earnings Per Share, Basic, Undistributed	$ (0.14)	$ 0.16	$ 1.57	$ 2.23
Basic net income per common share	$ 0.08	$ 0.16	$ 2.45	$ 2.23
Earnings Per Share, Diluted, Distributed	$ 0.22	$ 0.00	$ 0.88	$ 0.00
Earnings Per Share, Diluted, Undistributed	$ (0.14)	$ 0.16	$ 1.55	$ 2.22
Diluted net income per common share	$ 0.08	$ 0.16	$ 2.43	$ 2.22