Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Quarterly Financial Data [Abstract]
Total revenues	$ 354,359		$ 345,987		$ 296,855		$ 246,054		$ 212,880		$ 197,261		$ 175,132		$ 142,966		$ 1,243,255		$ 728,239		$ 526,627
Segment profits	138,990		136,647		111,538		89,968		71,807		59,051		53,588		36,933		477,143		221,379		137,039
Income from continuing operations	22,511		26,595		16,550		(18,493)		(1,968)		(9,332)		(10,672)		(21,591)		47,163		(43,563)
Net income available to common stockholders	$ 22,511		$ 26,595		$ 16,550		$ (18,493)		$ (1,968)		$ (9,332)		$ (10,672)		$ (21,591)		$ 47,163		$ (43,563)		$ (253,538)
Basic earnings per share of common stock, Net income available to common stockholders	$ 0.55	[1]	$ 0.66	[1]	$ 0.41	[1]	$ (0.46)	[1]	$ (0.05)	[1]	$ (0.23)	[1]	$ (0.27)	[1]	$ (0.54)	[1]	$ 1.17	[1]	$ (1.10)	[1]	$ (6.39)
Diluted earnings per share of common stock, Net income (loss) available to common stockholders	$ 0.54	[1]	$ 0.64	[1]	$ 0.40	[1]	$ (0.46)	[1]	$ (0.05)	[1]	$ (0.23)	[1]	$ (0.27)	[1]	$ (0.54)	[1]	$ 1.14	[1]	$ (1.10)	[1]	$ (6.39)
Weighted average common shares outstanding, Basic	40,658,000		40,451,000		40,356,000		39,884,000		39,776,000		39,743,000		39,724,000		39,621,000		40,375,013		39,714,053		39,684,231
Weighted average common shares outstanding, Diluted	41,307,000		41,396,000		41,336,000		39,884,000		39,776,000		39,743,000		39,724,000		39,621,000		41,536,629		39,714,053		39,684,231

[1] The sum of individual quarterly net income per share may not agree to the total for the year due to each period's computation being based on the weighted average number of common shares outstanding during each period.