Schedule IV - Changes in Mortgage Loans Excluding Unamortized Loan Issue Costs (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Mortgage Loans on Real Estate [Abstract]
Balance at beginning of year	$ 388,650us-gaap_MortgageLoansOnRealEstate	$ 368,650us-gaap_MortgageLoansOnRealEstate	$ 165,000us-gaap_MortgageLoansOnRealEstate
New mortgage loans and additional advances on existing loans	12,500	20,000	203,650
Mortgage loans on real estate including additions during year	401,150	388,650	368,650
Collection of principal	(3,650)
Deductions during year	(3,650)
Balance at end of year	$ 397,500us-gaap_MortgageLoansOnRealEstate	$ 388,650us-gaap_MortgageLoansOnRealEstate	$ 368,650us-gaap_MortgageLoansOnRealEstate

Total carrying amount of mortgage loans as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 10

-Section S99

-Paragraph 6

-Subparagraph (SX 210.5-04.(c) Schedule IV)

-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 29

-Article 12

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph c

-Subparagraph Schedule IV

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-29.6)

-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

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- Definition

The amount of principal collected on mortgage loans on real estate during the reporting period.

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- Definition

Total amount of new mortgage loans on real estate during the reporting period.

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- Definition

Total amount of additions to mortgage loans other than new loans during the reporting period.

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- Definition

The total periodic movement (increases and decreases) in the carrying amount of mortgage loans on real estate.

+ References

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