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Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing Number of Contracts

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Amount of the contractual principal due as of the balance sheet date of the mortgage loan (face amount).

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Mortgage Loans on Real Estate, Gross, Commercial and Consumer, Net

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Represents the number of mortgage loans individually impaired.

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Recorded investment in financing receivables that are 90 days or more past due and still accruing.

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Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

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Amount of loan with fixed rate of interest.

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Amount of decrease in investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, from foreclosure.

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MORTGAGE LOAN RECEIVABLES - Additional Information (Details)	3 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($)	Mar. 31, 2018	Dec. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Realized gain on sale of mortgage loan receivables			$ 0	$ 0	$ 0
Outstanding face amount			3,522,286,000	3,533,236,000
Unamortized discounts included in mortgage loan receivables held for investment, at amortized cost			$ 500,000	$ 200,000
Number of mortgage loans impaired \| loan			0	0
Provision for loan losses			$ 13,900,000	$ 0	300,000
Loans in default, no losses expected			17,600,000
Loans nonaccrual status, amount			36,850,000	26,850,000	0
First mortgage loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding face amount			3,192,160,000	3,140,788,000
Mortgage loan receivables held for investment, net, at amortized cost
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding face amount			3,340,381,000	3,300,709,000
Carrying value			3,318,390,000	3,282,462,000
Loans receivable with fixed rates of interest			$ 816,800,000	$ 723,700,000
Percentage of loans receivable with fixed rates of interest			24.60%	22.00%
Loans receivable with variable rates of interest			$ 2,500,000,000	$ 2,600,000,000
Loans receivable with variable rates of interest, percentage			75.40%	78.00%
Mortgage loan receivables held for sale
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Realized gain on sale of mortgage loan receivables			$ 0	$ 0	$ 0
Outstanding face amount			181,905,000	232,527,000
Loans receivable with fixed rates of interest			$ 182,400,000	$ 230,200,000
Percentage of loans receivable with fixed rates of interest			100.00%	100.00%
Loan on non-accrual status
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Loans nonaccrual status, amount			$ 0	$ 0
Minimum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Direct capitalization rate		4.70%	4.60%	4.35%
Maximum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Direct capitalization rate		5.00%	4.90%	4.65%
One Of Company Loans \| Mortgage loan receivables held for investment, net, at amortized cost
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Loans in default, carrying value	$ 45,000,000
One Of Company Loans \| Minimum \| Mortgage loan receivables held for investment, net, at amortized cost
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Percentage of equity kicker not subject to investment	19.00%
One Of Company Loans \| Maximum \| Mortgage loan receivables held for investment, net, at amortized cost
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Percentage of equity kicker not subject to investment	25.00%
Two Of Company Loans \| Mortgage loan receivables held for investment, net, at amortized cost
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Reserve based on targeted percentage level in portfolio			$ 1,200,000
Allowance for Loan and Lease Losses, Provision For Loss Resulting From On-going Bankruptcy Proceedings			$ 2,700,000
Number or loans in default \| loan			2
Loans in default, carrying value			$ 26,900,000
Series A \| One Of Company Loans \| Mortgage loan receivables held for investment, net, at amortized cost
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Loans in default, carrying value	$ 35,000,000
Series B \| One Of Company Loans \| Mortgage loan receivables held for investment, net, at amortized cost
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Loans in default, carrying value	$ 10,000,000