Loans - Ratings (Details)	3 Months Ended
Mar. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($)
Investments in loans
Total gross loans	$ 6,615,568,000	$ 5,956,062,000
Total gross loans (as a percent)	100.00%	100.00%
Number of impaired individual mortgage loans held-for-investment \| loan	0
Amount of loan impairment charges on individual loans held-for-investment	$ 0
Carrying amount of loans 90 days or more past due	0
Rating 1
Investments in loans
Total gross loans	$ 868,000	$ 921,000
Rating 1 \| Maximum
Investments in loans
LTV (as a percent)	65.00%
Rating 2
Investments in loans
Total gross loans	$ 1,514,519,000	$ 1,349,603,000
Total gross loans (as a percent)	22.90%	22.60%
Rating 2 \| Maximum
Investments in loans
LTV (as a percent)	70.00%
Rating 3
Investments in loans
Total gross loans	$ 4,260,376,000	$ 4,025,809,000
Total gross loans (as a percent)	64.40%	67.60%
Rating 3 \| Maximum
Investments in loans
LTV (as a percent)	80.00%
Rating 4
Investments in loans
Total gross loans	$ 442,682,000	$ 458,133,000
Total gross loans (as a percent)	6.70%	7.70%
Allowance for loan losses as a percent of carrying amount	1.50%
Rating 4 \| Minimum
Investments in loans
LTV (as a percent)	80.00%
Rating 4 \| Maximum
Investments in loans
LTV (as a percent)	90.00%
Rating 5
Investments in loans
Total gross loans	$ 56,857,000	$ 58,317,000
Total gross loans (as a percent)	0.90%	1.00%
Allowance for loan losses as a percent of carrying amount	5.00%
Rating 5 \| Minimum
Investments in loans
LTV (as a percent)	90.00%
N/A
Investments in loans
Total gross loans	$ 340,266,000	$ 63,279,000
Total gross loans (as a percent)	5.10%	1.10%
Total loans held-for-investment
Investments in loans
Total gross loans	$ 6,240,302,000	$ 5,857,783,000
Total loans held-for-investment \| First Mortgages, excluding Cost Recovery Loans
Investments in loans
Total gross loans	5,212,199,000	4,865,994,000
Total loans held-for-investment \| First Mortgages, excluding Cost Recovery Loans \| Rating 1
Investments in loans
Total gross loans	868,000	921,000
Total loans held-for-investment \| First Mortgages, excluding Cost Recovery Loans \| Rating 2
Investments in loans
Total gross loans	1,241,424,000	1,092,731,000
Total loans held-for-investment \| First Mortgages, excluding Cost Recovery Loans \| Rating 3
Investments in loans
Total gross loans	3,529,411,000	3,348,874,000
Total loans held-for-investment \| First Mortgages, excluding Cost Recovery Loans \| Rating 4
Investments in loans
Total gross loans	383,639,000	365,151,000
Total loans held-for-investment \| First Mortgages, excluding Cost Recovery Loans \| Rating 5
Investments in loans
Total gross loans	56,857,000	58,317,000
Total loans held-for-investment \| Subordinated mortgages
Investments in loans
Total gross loans	294,754,000	278,032,000
Total loans held-for-investment \| Subordinated mortgages \| Rating 2
Investments in loans
Total gross loans	27,280,000	27,069,000
Total loans held-for-investment \| Subordinated mortgages \| Rating 3
Investments in loans
Total gross loans	267,474,000	250,963,000
Total loans held-for-investment \| Mezzanine Loans
Investments in loans
Total gross loans	733,349,000	713,757,000
Total loans held-for-investment \| Mezzanine Loans \| Rating 2
Investments in loans
Total gross loans	210,815,000	194,803,000
Total loans held-for-investment \| Mezzanine Loans \| Rating 3
Investments in loans
Total gross loans	463,491,000	425,972,000
Total loans held-for-investment \| Mezzanine Loans \| Rating 4
Investments in loans
Total gross loans	59,043,000	92,982,000
Loans held-for-sale
Investments in loans
Total gross loans	340,266,000	63,279,000
Loans held-for-sale \| N/A
Investments in loans
Total gross loans	340,266,000	63,279,000
Loans transferred as secured borrowings
Investments in loans
Total gross loans	35,000,000	35,000,000
Loans transferred as secured borrowings \| Rating 2
Investments in loans
Total gross loans	$ 35,000,000	$ 35,000,000

Represents the amount of impairment charges on individual mortgage loans of real estate that are held for investment.

No definition available.

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- Definition

Represents the range of loan to value ratio that is used to classify a loan into a particular credit rating category.

+ References

No definition available.

+ Details

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- Definition

Represents the allowance for loan losses as a percent of carrying amount.

+ References

No definition available.

+ Details

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- Definition

The gross carrying amount of the outstanding balance due under the mortgage loan.

+ References

No definition available.

+ Details

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- Definition

The gross carrying amount of the outstanding balance due under the mortgage loan as a percentage of total loans.

+ References

No definition available.

+ Details

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- Definition

Represents the number of impaired individual mortgage loans on real estate that are held for investment.

+ References

No definition available.

+ Details

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5111-111524

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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