Certain Long-Duration Contracts with Guarantees (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Net Amount at Risk by Product and Guarantee [Line Items]
Deferred sales inducements	$ 0	$ 0
Annuity Contracts \| Market Value Adjusted
Net Amount at Risk by Product and Guarantee [Line Items]
General Account Investment Option	$ 3,500,000	$ 3,400,000

Amount of deferred sale inducement cost capitalized on contract remaining in force.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 30
-Section 50
-Paragraph 2B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117419109&loc=SL117422543-158416

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6481654&loc=d3e11214-158414

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=117419109&loc=d3e11332-158416

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(1)
-URI http://asc.fasb.org/extlink&oid=117419843&loc=SL117420844-207641

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