Investments (excluding Consolidated Investment Entities) - Mortgages by Year of Origination (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investment [Line Items]
Total Commercial mortgage loans	$ 8,678	$ 8,689
2018
Investment [Line Items]
Total Commercial mortgage loans	741	0
2017
Investment [Line Items]
Total Commercial mortgage loans	1,517	1,525
2016
Investment [Line Items]
Total Commercial mortgage loans	1,446	1,428
2015
Investment [Line Items]
Total Commercial mortgage loans	1,077	1,250
2014
Investment [Line Items]
Total Commercial mortgage loans	1,215	1,303
2013
Investment [Line Items]
Total Commercial mortgage loans	1,157	1,287
2012 and prior
Investment [Line Items]
Total Commercial mortgage loans	$ 1,525	$ 1,896

Amount before allowance of commercial loans issued to businesses to acquire, develop, construct, improve, or refinance land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5066-111524

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant