Total Invested Assets and Related Net Investment Income - Changes in Asset Fair Value and Currency Change (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Disclosure of fair value measurement of assets [line items]
Increase (decrease) in fair value of financial assets designated as measured at fair value through profit or loss, attributable to changes in credit risk of financial assets	$ 7,162	$ (4,376)
Fair value changes on investment properties	305	529
Foreign exchange gains (losses)	(349)	446
Realized gains (losses) on property and equipment	0	28
Fair value and foreign currency changes on assets and liabilities	7,118	(3,373)
Gain on sale of operating lease	28
Cash, cash equivalents and short-term securities
Disclosure of fair value measurement of assets [line items]
Increase (decrease) in fair value of financial assets designated as measured at fair value through profit or loss, attributable to changes in credit risk of financial assets	(2)	8
Debt securities
Disclosure of fair value measurement of assets [line items]
Increase (decrease) in fair value of financial assets designated as measured at fair value through profit or loss, attributable to changes in credit risk of financial assets	5,686	(2,704)
Equity securities
Disclosure of fair value measurement of assets [line items]
Increase (decrease) in fair value of financial assets designated as measured at fair value through profit or loss, attributable to changes in credit risk of financial assets	629	(401)
Derivative assets
Disclosure of fair value measurement of assets [line items]
Increase (decrease) in fair value of financial assets designated as measured at fair value through profit or loss, attributable to changes in credit risk of financial assets	772	(1,295)
Other invested assets
Disclosure of fair value measurement of assets [line items]
Increase (decrease) in fair value of financial assets designated as measured at fair value through profit or loss, attributable to changes in credit risk of financial assets	$ 77	$ 16

The increase (decrease) in the fair value of a financial asset (or group of financial assets) designated as measured at fair value through profit or loss that is attributable to changes in the credit risk of that asset determined either: (a) as the amount of change in its fair value that is not attributable to changes in market conditions that give rise to market risk ; or (b) using an alternative method the entity believes more faithfully represents the amount of change in its fair value that is attributable to changes in the credit risk of the asset. [Refer: Credit risk [member]; Financial assets]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2019-01-01
-Paragraph 9
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2019-en-r&anchor=para_9_c&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_ChangesInFairValueOfFinancialAssetsAttributableToChangesInCreditRiskOfFinancialAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfFairValueMeasurementOfAssetsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The gains (losses) on disposals of property, plant and equipment. [Refer: Property, plant and equipment]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 98
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_98_c&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_GainsLossesOnDisposalsOfPropertyPlantAndEquipment
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of exchange differences recognised in profit or loss that arise from foreign currency transactions, excluding those arising on financial instruments measured at fair value through profit or loss in accordance with IFRS 9. [Refer: At fair value [member]; Financial instruments, class [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 7
-IssueDate 2019-01-01
-Section A Statement of cash flows for an entity other than a financial institution
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=7&code=ifrs-tx-2019-en-r&doctype=Illustrative%20Examples&dita_xref=IAS07_IE_A_TI
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 21
-IssueDate 2019-01-01
-Paragraph 52
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=21&code=ifrs-tx-2019-en-r&anchor=para_52_a&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_GainsLossesOnExchangeDifferencesOnTranslationRecognisedInProfitOrLoss
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The gains (losses) recognised in profit or loss for assets measured at fair value that are attributable to the change in unrealised gains or losses relating to those assets held at the end of the reporting period. [Refer: At fair value [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2019-01-01
-Paragraph 93
-Subparagraph f
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=13&code=ifrs-tx-2019-en-r&anchor=para_93_f&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_GainsLossesRecognisedInProfitOrLossAttributableToChangeInUnrealisedGainsOrLossesForAssetsHeldAtEndOfPeriodFairValueMeasurement
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Gain (Loss) on Termination of Lease

+ References

No definition available.

+ Details

Name:	slf_GainLossonTerminationofLease
Namespace Prefix:	slf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Increase (Decrease) In Asset Fair Value, Investment Property

+ References

No definition available.

+ Details

Name:	slf_IncreaseDecreaseInAssetFairValueInvestmentProperty
Namespace Prefix:	slf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	ifrs-full_ClassesOfAssetsAxis=slf_CashCashEquivalentsAndShortTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfAssetsAxis=ifrs-full_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfAssetsAxis=slf_EquitySecurities1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfAssetsAxis=ifrs-full_DerivativesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfAssetsAxis=slf_OtherInvestedAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: