Amount of principal due on loans that have been delinquent, which may exclude loans having interest delinquent for three months or less, 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 FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29.10(a))
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Name:	us-gaap_MortgageLoansOnRealEstatePrincipalAmountOfDelinquentLoans
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Delinquency Statistics of Commercial Real Estate Loan (Parenthetical) (Detail) - USD ($) $ in Thousands	Aug. 08, 2016	Jun. 30, 2016	Dec. 31, 2015
Mortgage Loans On Real Estate [Line Items]
Delinquency statistics, Total		$ 1,496,821	$ 1,627,121
Commercial mortgage loans
Mortgage Loans On Real Estate [Line Items]
Delinquency statistics, Total		1,315,301	1,427,328
90 days or more
Mortgage Loans On Real Estate [Line Items]
Delinquency statistics, Total		$ 1,162	$ 1,163
Subsequent Event \| 90 days or more \| Commercial mortgage loans
Mortgage Loans On Real Estate [Line Items]
Delinquency statistics, Total	$ 74,800