Notes and Other Receivables (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 48,053		$ 66,369
Stated interest rate (in hundredths)	5.50%
Secured Due January 2012 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	0		7,331
Stated interest rate (in hundredths)	9.80%
Secured Due November 2012 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	0	[1]	12,428	[1]
Stated interest rate (in hundredths)	5.00%
Secured 1 Due December 2012 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	10,921		10,928
Interest rate floor (in hundredths)	8.00%
Secured 2 Due December 2012 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	6,397		6,422
Stated interest rate (in hundredths)	8.80%
Secured Due November 2013 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	971		971
Stated interest rate (in hundredths)	8.00%
Secured Due December 2014 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	3,199		3,221
Stated interest rate (in hundredths)	6.50%
Secured Due June 2017 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	17,870		17,646
Stated interest rate (in hundredths)	6.30%
Notes Receivable From Affiliates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	3,705		2,734
Other Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 4,990		$ 4,688

[1] The note receivable was contributed to the Elkhorn co-investment, as discussed in Note 2, during the first quarter of 2012.