Loans Receivable and Other Lending Investments, net (Impaired Loans) (Details) - USD ($)	3 Months Ended	12 Months Ended
Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Impaired Loans
Impaired loans with allowance recorded, Recorded Investment		$ 66,725,000	$ 237,877,000
Impaired loans with allowance recorded, Unpaid Principal Balance		66,777,000	227,280,000
Impaired loans, Related Allowance		(40,395,000)	(60,989,000)
Impaired loans with no related allowance recorded, Average Recorded Investment		0	6,582,000	$ 10,460,000
Impaired loans with no related allowance recorded, Interest Income Recognized		301,000	1,127,000	226,000
Impaired loans with allowance recorded, Average Recorded Investment		106,210,000	239,505,000	185,022,000
Impaired loans with allowance recorded, Interest Income Recognized		0	0	0
Impaired loans, Average Recorded Investment		106,210,000	246,087,000	195,482,000
Impaired loans, Interest Income Recognized		301,000	1,127,000	226,000
Gross carrying value of loan		919,493,000	1,289,568,000
Preferred equity investment received, face value	$ 100,000,000
Preferred equity investment mandatory redemption period (in years)	5 years
Preferred equity investment received, recorded fair value	$ 77,000,000
Provision for (recovery of) loan losses		16,937,000
Nonperforming Financial Instruments
Impaired Loans
Impaired loans, Interest Income Recognized		0	0	0
Senior mortgages
Impaired Loans
Impaired loans with allowance recorded, Recorded Investment		66,725,000	81,343,000
Impaired loans with allowance recorded, Unpaid Principal Balance		66,777,000	81,431,000
Impaired loans, Related Allowance		(40,395,000)	(48,518,000)
Impaired loans with no related allowance recorded, Average Recorded Investment		0	0	3,661,000
Impaired loans with no related allowance recorded, Interest Income Recognized		0	0	226,000
Impaired loans with allowance recorded, Average Recorded Investment		67,041,000	82,749,000	118,921,000
Impaired loans with allowance recorded, Interest Income Recognized		0	0	0
Impaired loans, Average Recorded Investment		67,041,000	82,749,000	122,582,000
Impaired loans, Interest Income Recognized		0	0	226,000
Gross carrying value of loan		760,749,000	791,152,000
Subordinate mortgages
Impaired Loans
Impaired loans with no related allowance recorded, Average Recorded Investment		0	6,582,000	6,799,000
Impaired loans with no related allowance recorded, Interest Income Recognized		301,000	1,127,000	0
Impaired loans, Average Recorded Investment		0	6,582,000	6,799,000
Impaired loans, Interest Income Recognized		301,000	1,127,000	0
Gross carrying value of loan		10,161,000	9,495,000
Corporate/Partnership loans
Impaired Loans
Impaired loans with allowance recorded, Recorded Investment		0	156,534,000
Impaired loans with allowance recorded, Unpaid Principal Balance		0	145,849,000
Impaired loans, Related Allowance		0	(12,471,000)
Impaired loans with allowance recorded, Average Recorded Investment		39,169,000	156,756,000	66,101,000
Impaired loans with allowance recorded, Interest Income Recognized		0	0	0
Impaired loans, Average Recorded Investment		39,169,000	156,756,000	66,101,000
Impaired loans, Interest Income Recognized		0	0	$ 0
Gross carrying value of loan		$ 148,583,000	$ 488,921,000
Corporate/Partnership loans \| Nonperforming Financial Instruments
Impaired Loans
Gross carrying value of loan	145,800,000
Proceeds from collection of loan receivable	45,800,000
Provision for (recovery of) loan losses	$ 21,400,000

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Impaired Financing Receivable [Abstract]

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The interest income recognized on a cash-basis or accrual method of accounting during the time within that period that the financing receivables were impaired.

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Reflects the aggregate gross carrying amount of all categories of loans held in portfolio, after deducting deferred income, but before deducting the allowance for losses on loans.

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Amount of allowance for credit losses related to recorded investment.

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Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses.

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Amount of average investment of impaired financing receivables for which there is a related allowance for credit losses.

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Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.

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The cash inflow associated with the collection, including prepayments, of loans receivable issued for financing of goods and services.

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Amount of expense related to loss from loan transactions.

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