Investments Mortgage Loans Credit Ratings Indicator (Details) - Commercial Real Estate [Member] - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Mortgage loans	$ 1,338	$ 1,361
Category 1 [Member]
Mortgage loans	41	42
Category 2 to 4 [Member]
Mortgage loans	1,283	1,301
Categories 5 and 6 [Member]
Mortgage loans	14	18
Category 7 [Member]
Mortgage loans	$ 0	$ 0

Amount of 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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G))
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

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