Loans Receivable and Investments 2017 Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gains (losses) on real estate loan investments	$ 13,202	$ 124	$ 2,271
Secured Mortgage Loans and Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gains (losses) on real estate loan investments		600
Partial Payments of Loan Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from collection of loans receivable		37,600
Full Repayments on Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from collection of loans receivable	862,900	$ 35,500
Gains (losses) on real estate loan investments	$ 27,800
LHP | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable				$ 700,000
Revolving Credit Facility | LHP | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable				$ 60,000