Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of unamortized debt discount (premium) and debt issuance costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: 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(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=rga_SeniorNotesDue2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rga_SeniorNotesDue2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rga_SeniorNotesDue2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rga_SeniorNotesDue2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rga_SeniorNotesDue2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rga_SubordinatedDebenturesDue2042Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rga_SubordinatedDebenturesDue2056Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rga_JuniorSubordinatedDebenturesDue2065Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_NotesPayableToBanksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt (Schedule of Long-term Debt Instruments) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2006
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 2,808,770,000	$ 3,110,853,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	20,405,000	22,218,000
Debt Instrument, Face Amount			$ 850,000,000.0
Long-term debt	2,788,365,000	3,088,635,000
Senior Notes Due 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	0	299,945,000
Debt Instrument, Face Amount	$ 300,000,000
Debt Instrument, Maturity Date	Dec. 31, 2017
Debt Instrument, Interest Rate, Stated Percentage	5.625%
Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 399,873,000	399,805,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2019
Debt Instrument, Interest Rate, Stated Percentage	6.45%
Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 399,245,000	399,025,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2021
Debt Instrument, Interest Rate, Stated Percentage	5.00%
Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 399,138,000	398,986,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2023
Debt Instrument, Interest Rate, Stated Percentage	4.70%
Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 399,987,000	399,985,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	8,800,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2026
Debt Instrument, Interest Rate, Stated Percentage	3.95%
Subordinated Debentures Due 2042 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 400,000,000	400,000,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2042
Debt Instrument, Interest Rate, Stated Percentage	6.20%
Subordinated Debentures Due 2056 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 400,000,000	400,000,000
Debt Instrument, Face Amount	$ 400,000,000.0
Debt Instrument, Maturity Date	Dec. 31, 2056
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Junior Subordinated Debentures Due 2065 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 318,740,000	318,737,000
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Maturity Date	Dec. 31, 2065
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 91,787,000	$ 94,370,000
Debt Instrument, Face Amount	$ 100,000,000
Debt Instrument, Maturity Date	Dec. 31, 2039
Debt Instrument, Interest Rate, Stated Percentage	4.09%