Property Acquisitions, Discontinued Operations, And Assets Held For Sale Property Acquisitions, Discontinued Operations, And Assets Held For Sale (Pro Forma Consolidated Income Statement Information) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Property Acquisitions, Discontinued Operations, And Assets Held For Sale [Abstract]
Property revenues	$ 181,598	$ 168,581
Property expenses	68,759	67,070
Property results	$ 112,839	$ 101,511