Business Segment Information (Reconciliation Of Segment Margin To (Loss) Income Before Income Taxes) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Business Segment Information [Abstract]
Segment margin	$ 202,501	[1]	$ 149,564	$ 134,490
Corporate general and administrative expenses	(31,685)		(110,058)	(36,475)
Depreciation, amortization and impairment	(61,926)		(53,557)	(67,586)
Net loss on disposal of surplus assets	(264)		(12)	(160)
Interest expense	(35,767)		(22,924)	(13,660)
Distributable cash from equity investees in excess of equity in earnings	(16,681)		(2,284)	496
Non-cash items not included in segment margin	(1,531)		(4,479)	(4,089)
Cash payments from direct financing leases in excess of earnings	(4,615)		(4,203)	(3,758)
Income (loss) before income taxes	$ 50,032		$ (47,953)	$ 9,258

[1] A reconciliation of Segment Margin to income (loss) before income taxes for each year presented is as follows: