Investments (Investments in Fixed Maturity and Equity Securities Available-for-Sale by Sector) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 21,418,741	$ 18,924,711
Estimated Fair Value	$ 22,535,830	$ 19,619,084
% of Total	100.00%	100.00%
Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 33,889,968	$ 30,211,787
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2,650,578	2,243,037
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	158,804	361,199
Estimated Fair Value	$ 36,381,742	$ 32,093,625
% of Total	100.00%	100.00%
Other-than-temporary impairments in AOCI	$ 275	$ 100
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	116,392	285,579
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	945	3,440
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4,406	13,658
Estimated Fair Value	$ 112,931	$ 275,361
% of Total	100.00%	100.00%
Corporate Debt Securities [Member] \| Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 21,418,741	$ 18,924,711
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,209,999	911,618
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	92,910	217,245
Estimated Fair Value	$ 22,535,830	$ 19,619,084
% of Total	61.90%	61.10%
Other-than-temporary impairments in AOCI	$ 0	$ 0
Canadian and Canadian provincial governments \| Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,850,982	2,561,605
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,142,635	1,085,982
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2,432	3,541
Estimated Fair Value	$ 3,991,185	$ 3,644,046
% of Total	11.00%	11.40%
Other-than-temporary impairments in AOCI	$ 0	$ 0
Residential mortgage-backed securities \| Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,645,379	1,258,039
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	42,202	33,917
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	8,276	13,380
Estimated Fair Value	$ 1,679,305	$ 1,278,576
% of Total	4.60%	4.00%
Other-than-temporary impairments in AOCI	$ 0	$ 375
Asset-backed securities \| Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,680,918	1,443,822
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	18,713	9,350
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	5,063	23,828
Estimated Fair Value	$ 1,694,568	$ 1,429,344
% of Total	4.70%	4.50%
Other-than-temporary impairments in AOCI	$ 275	$ 275
Commercial Mortgage Backed Securities [Member] \| Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,293,296	1,342,440
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	25,471	28,973
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	5,445	7,759
Estimated Fair Value	$ 1,313,322	$ 1,363,654
% of Total	3.60%	4.20%
Other-than-temporary impairments in AOCI	$ 0	$ 0
US Treasury and Government [Member] \| Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,621,053	1,518,702
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	13,614	12,644
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	30,998	63,044
Estimated Fair Value	$ 1,603,669	$ 1,468,302
% of Total	4.40%	4.60%
Other-than-temporary impairments in AOCI	$ 0	$ 0
US States and Political Subdivisions Debt Securities [Member] \| Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	614,099	566,761
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	52,919	37,499
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	5,987	12,464
Estimated Fair Value	$ 661,031	$ 591,796
% of Total	1.80%	1.80%
Other-than-temporary impairments in AOCI	$ 0	$ 0
Foreign Government Debt Securities [Member] \| Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,765,500	2,595,707
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	145,025	123,054
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	7,693	19,938
Estimated Fair Value	$ 2,902,832	$ 2,698,823
% of Total	8.00%	8.40%
Other-than-temporary impairments in AOCI	$ 0	$ 0
Nonredeemable Preferred Stock [Member] \| Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	41,878	55,812
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	312	1,648
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	3,289	6,337
Estimated Fair Value	$ 38,901	$ 51,123
% of Total	34.40%	18.60%
Other equity securities \| Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 74,514	$ 229,767
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	633	1,792
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1,117	7,321
Estimated Fair Value	$ 74,030	$ 224,238
% of Total	65.60%	81.40%

Percentage of available for sale securities

No definition available.

Name:	rga_PercentageOfTotalAvailableForSaleSecurities
Namespace Prefix:	rga_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Accumulated other comprehensive loss related to portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized as available-for-sale that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security. The amount represented by this item is net of tax, as applicable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 9A
-URI http://asc.fasb.org/extlink&oid=82896770&loc=SL6284427-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

+ Details

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

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

+ Details

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

- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
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 investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

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

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix:	us-gaap_
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

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_InvestmentTypeAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_NonredeemablePreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=rga_EquitySecuritiesOtherThanNonRedeemablePreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: