Notes Receivable and Allowance for Losses - Past due balances of mezzanine and other notes receivable (Details) (Mezzanine & Other Notes Receivable [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
30-89 days Past Due	$ 0	$ 0
Greater than 90 days Past Due	47	9,676
Total Past Due	47	9,676
Current	17,963	25,933
Total Mezzanine and Other Notes Receivables	18,010	35,609
Senior [Member]
Financing Receivable, Recorded Investment [Line Items]
30-89 days Past Due	0	0
Greater than 90 days Past Due	0	0
Total Past Due	0	0
Current	10,152	18,052
Total Mezzanine and Other Notes Receivables	10,152	18,052
Subordinated [Member]
Financing Receivable, Recorded Investment [Line Items]
30-89 days Past Due	0	0
Greater than 90 days Past Due	0	9,629
Total Past Due	0	9,629
Current	3,863	4,523
Total Mezzanine and Other Notes Receivables	3,863	14,152
Unsecured [Member]
Financing Receivable, Recorded Investment [Line Items]
30-89 days Past Due	0	0
Greater than 90 days Past Due	47	47
Total Past Due	47	47
Current	3,948	3,358
Total Mezzanine and Other Notes Receivables	$ 3,995	$ 3,405