Financial assets and liabilities at fair value - Fair value related to credit risk (Details) - SEK (kr) kr in Millions	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
CVA/DVA, net
Fair value related to credit risk
Fair value originating from credit risk (- liabilities increase/ + liabilities decrease)	kr (16)		kr (17)
The period's change in fair value originating from credit risk (+ income/ - loss)	1	kr 5
OCA
Fair value related to credit risk
Fair value originating from credit risk (- liabilities increase/ + liabilities decrease)	320		kr 265
The period's change in fair value originating from credit risk (+ income/ - loss)	kr 55	kr 97

The accumulated increase (decrease) in the fair value of financial liabilities that is attributable to changes in the credit risk of the liabilities. [Refer: Credit risk [member]; Market risk [member]; Increase (decrease) in fair value of financial liability, attributable to changes in credit risk of liability]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2024-01-01
-Paragraph 10
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2024-en-r&anchor=para_10_a&doctype=Standard
-URIDate 2024-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2024-01-01
-Paragraph 10A
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2024-en-r&anchor=para_10A_a&doctype=Standard
-URIDate 2024-03-27

Name:	ifrs-full_AccumulatedChangesInFairValueOfFinancialLiabilityAttributableToChangesInCreditRiskOfLiability
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant