Reinsurance (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Ceded Credit Risk [Line Items]
Reinsurance Claims Recoverables	$ 269.1	$ 243.8
Claims Recoverable From Retrocessionaires Past Due	$ 6.7	$ 1.9
AM Best, A- Rating [Member]
Ceded Credit Risk [Line Items]
Ceded Credit Risk, Disclosure	“A- (excellent)”	“A- (excellent)”
AM Best, B++ Rating [Member]
Ceded Credit Risk [Line Items]
Ceded Credit Risk, Disclosure	B++

Represents the amount of claims paid by the company and recoverable from retrocessionaires which is contractually past due in excess of 90 days.

No definition available.

+ Details

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Namespace Prefix:	rga_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The known and estimated amount recoverable as of the balance sheet date from reinsurers for claims paid or incurred by the ceding insurer and associated claims settlement expenses, including estimated amounts for claims incurred but not reported, and policy benefits, net of any related valuation allowance.

+ References

No definition available.

+ Details

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Namespace Prefix:	rga_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Description of ceding entity's credit risk concentration associated with reinsurance recoverable and prepaid reinsurance premium. Includes, but is not limited to, concentration of activity, region, or economic characteristic.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 825
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=99380617&loc=SL75241803-196195

+ Details

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- Details

Name:	srt_CreditRatingAMBestAxis=srt_AMBestAMinusRatingMember
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- Details

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