Noncontrolling Interests (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Noncontrolling Interests (Textual) [Abstract]
Ownership interest percentage to consolidate partnerships	Equal to or greater than 50.1%
Net income attributable to noncontrolling interests	$ 4,455,000	$ 3,915,000	$ 4,158,000
Noncontrolling interests	10,074,000	10,561,000
Mandatorily Redeemable Noncontrolling Interests included in other liabilities	$ 3,100,000	$ 1,700,000
Noncontrolling Interest, Ownership Percentage by Parent	50.10%