Business Segment Information (Reconciliation Of Segment Margin To (Loss) Income Before Income Taxes) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Business Segment Information [Abstract]
Segment margin	$ 60,252	[1]	$ 49,155	[1]
Corporate general and administrative expenses	(8,621)		(7,384)
Depreciation and amortization	(15,035)		(13,903)
Net loss on disposal of surplus assets	256		11
Interest expense	(10,596)		(8,699)
Distributable cash from equity investees in excess of equity in earnings	(6,733)		(3,303)
Non-cash items not included in segment margin	1,324		(7,434)
Cash payments from direct financing leases in excess of earnings	(1,221)		(1,113)
Income before income taxes	$ 19,626		$ 7,330

[1] A reconciliation of Segment Margin to income before income taxes for the periods presented is as follows: