Investments in Unconsolidated Companies (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			6 Months Ended
	Dec. 31, 2012 entities	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2010 Dugan Realty [Member]
Schedule of Equity Method Investments [Line Items]
Rental revenue	$ 291,534	$ 272,937	$ 228,378	$ 42,500
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	$ 3,125	$ 10,709	$ 19,202	$ 6,400
Number of unconsolidated joint ventures in which equity interests held	20