Investments (Investments in Fixed Maturity and Equity Securities Available-for-Sale by Sector) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 31	$ 20
Available for Sale at Fair value - Amortized cost	55,873	49,548
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	$ 60,749	$ 56,735
Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	100.00%	100.00%
Financing Receivable, Allowance for Credit Loss	$ 31	$ 20
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	349	197
Available for Sale at Fair value - Amortized cost	55,873	49,548
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	60,749	56,735
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5,256	7,404
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	35,239	31,963
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	$ 38,103	$ 36,208
Corporate Debt Securities [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	62.80%	63.90%
Financing Receivable, Allowance for Credit Loss	$ 26	$ 17
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	194	94
Available for Sale at Fair value - Amortized cost	35,239	31,963
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	38,103	36,208
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3,084	4,356
Canadian Provincial Governments [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	$ 4,944	$ 5,140
Canadian Provincial Governments [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	8.10%	9.10%
Financing Receivable, Allowance for Credit Loss	$ 0	$ 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	0
Available for Sale at Fair value - Amortized cost	3,339	3,145
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	4,944	5,140
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,606	1,995
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	$ 1,050	$ 1,817
Residential Mortgage Backed Securities [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	1.70%	3.20%
Financing Receivable, Allowance for Credit Loss	$ 0	$ 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	7	2
Available for Sale at Fair value - Amortized cost	1,020	1,735
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	1,050	1,817
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	37	84
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	$ 4,005	$ 3,092
Asset-backed Securities [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	6.60%	5.40%
Financing Receivable, Allowance for Credit Loss	$ 0	$ 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	41	42
Available for Sale at Fair value - Amortized cost	4,024	3,099
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	4,005	3,092
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	22	35
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	$ 1,849	$ 1,868
Commercial Mortgage Backed Securities [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	3.00%	3.30%
Financing Receivable, Allowance for Credit Loss	$ 1	$ 3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	6	21
Available for Sale at Fair value - Amortized cost	1,790	1,790
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	1,849	1,868
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	66	102
US Treasury and Government [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	$ 2,105	$ 1,437
US Treasury and Government [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	3.50%	2.50%
Financing Receivable, Allowance for Credit Loss	$ 0	$ 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	8	1
Available for Sale at Fair value - Amortized cost	2,082	1,242
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	2,105	1,437
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	31	196
US States and Political Subdivisions Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	$ 1,323	$ 1,390
US States and Political Subdivisions Debt Securities [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	2.20%	2.40%
Financing Receivable, Allowance for Credit Loss	$ 0	$ 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5	4
Available for Sale at Fair value - Amortized cost	1,191	1,237
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	1,323	1,390
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	137	157
Debt Security, Government, Non-US [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	$ 7,370	$ 5,783
Debt Security, Government, Non-US [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	12.10%	10.20%
Financing Receivable, Allowance for Credit Loss	$ 4	$ 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	87	33
Available for Sale at Fair value - Amortized cost	7,188	5,337
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	7,370	5,783
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	$ 273	$ 479

Percentage of available for sale securities

No definition available.

Name:	rga_PercentageOfTotalAvailableForSaleSecurities
Namespace Prefix:	rga_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563

+ Details

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

- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

+ Details

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

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124260329&loc=d3e26610-111562

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563

+ Details

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

- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7)(2))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (3)

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (c)

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (1)

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

Name:	us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_FixedMaturitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=rga_CanadianProvincialGovernmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: