Noncontrolling Interests (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Noncontrolling Interests [Abstract]
Net income adjusted for noncontrolling interests	$ 21,197	$ 16,096
Net increase in equity for the acquisition of noncontrolling interests		1,673
Change from net income adjusted for noncontrolling interests and transfers from the noncontrolling interests	$ 21,197	$ 17,769