Business Segment Information (Reconciliation Of Segment Margin To (Loss) Income Before Income Taxes) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting [Abstract]
Segment margin	$ 70,442	$ 62,831	$ 142,507	$ 123,083
Corporate general and administrative expenses	(10,305)	(8,707)	(21,142)	(17,328)
Depreciation and amortization	(15,670)	(15,830)	(30,723)	(30,609)
Interest expense	(12,254)	(10,228)	(23,695)	(20,824)
Distributable cash from equity investees in excess of equity in earnings	(4,891)	(6,752)	(11,455)	(13,485)
Non-cash items not included in segment margin	960	(1,577)	(3,335)	(253)
Cash payments from direct financing leases in excess of earnings	(1,263)	(1,249)	(2,495)	(2,470)
Income before income taxes	$ 27,019	$ 18,488	$ 49,662	$ 38,114