Noncontrolling Interests (Preferred Stockholders' Equity in Subsidiaries) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Noncontrolling Interest [Line Items]
Preferred stock-perpetual voting variable term shares issued	300,000
Preferred stock-perpetual voting, dividend rate	6.125%
Preferred stock-perpetual voting, total issuance dollar value	$ 300,000,000
Minority Interest In Net Income Loss Preferred Unit Holders	4,594,000	4,543,000	9,188,000	9,137,000
Balance	$ 296,370,000		$ 296,370,000		$ 296,370,000