Mortgage Notes Receivable - Narrative (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) loan	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of mortgage notes receivable | loan		9
Principal repayments received from borrowers | $		$ 5,417,000	$ 6,921,000	$ 77,614,000
Reserve for loan loss | $	$ 15,300,000	$ 0	$ 15,300,000	$ 0
Mortgage notes receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of mortgage notes receivable | loan		9
Weighted-average interest rate		6.30%
Weighted-average years to maturity		13 years
Number of mortgage notes receivable repaid at maturity | loan		1
Principal repayments received from borrowers | $		$ 400,000
Number of mortgage notes with capitalized principal and interest | loan		1
Unsecured note reserve [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal repayments received from borrowers | $		$ 0