Fair Value - Carrying amount and estimated fair value of financial instrument assets and liabilities which are not measured at fair value (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Assets
Mortgage loans	$ 722,000,000	$ 591,000,000
Liabilities
Short term debt	150,000,000	0
Long term debt	2,707,000,000	2,710,000,000
Carrying Amount
Assets
Mortgage loans	722,000,000	591,000,000
Note receivable	45,000,000
Liabilities
Short term debt	150,000,000
Long term debt	2,707,000,000	2,710,000,000
Estimated Fair Value
Assets
Mortgage loans	731,000,000	594,000,000
Note receivable	46,000,000
Liabilities
Short term debt	152,000,000
Long term debt	2,916,000,000	2,952,000,000
Level 1 \| Estimated Fair Value
Assets
Mortgage loans	0	0
Note receivable	0
Liabilities
Short term debt	0
Long term debt	0	0
Level 2 \| Estimated Fair Value
Assets
Mortgage loans	0	0
Note receivable	0
Liabilities
Short term debt	152,000,000
Long term debt	2,916,000,000	2,952,000,000
Level 3 \| Estimated Fair Value
Assets
Mortgage loans	731,000,000	594,000,000
Note receivable	46,000,000
Liabilities
Short term debt	0
Long term debt	$ 0	$ 0

For an unclassified balance sheet, the amount due from customers or clients for goods or services that have been delivered or sold in the normal course of business, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(4))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(9))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(5))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- References

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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- Definition

Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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- Definition

The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(c))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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