Investment Information - Securities lending agreements (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Disclosure Investment Information [Abstract]
Fair value of cash collateral received on securities lending	$ 26,200	$ 81,200
Fair value of non-cash collateral received on securities lending	156,100	307,200
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	182,274	388,366
Gross amount of recognized liabilities for securities lending in offsetting disclosure in note 9	0	0
Amounts related to securities lending not included in offsetting disclosure in note 9	182,274	388,366
US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	158,691	356,305
Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	11,715	2,570
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	11,868	29,491
Overnight and continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	167,958	272,393
Overnight and continuous \| US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	144,375	240,332
Overnight and continuous \| Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	11,715	2,570
Overnight and continuous \| Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	11,868	29,491
Less than 30 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0	0
Less than 30 days \| US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0	0
Less than 30 days \| Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0	0
Less than 30 days \| Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0	0
30 - 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	14,316	115,973
30 - 90 days \| US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	14,316	115,973
30 - 90 days \| Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0	0
30 - 90 days \| Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0	0
90 days or more
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0	0
90 days or more \| US government and government agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0	0
90 days or more \| Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	0	0
90 days or more \| Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending payable	$ 0	$ 0

-- None. No documentation exists for this element. --

No definition available.

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- Definition

The fair value of collateral received by the entity associated with securities borrowed that must be returned if the counterparty fulfills its obligations. It appears on the balance sheet as a liability and has a corresponding asset that appears on the balance sheet called Securities Received as Collateral.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.15)
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

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- Definition

Amount of secured borrowings in excess of (less than) the liability for repurchase agreements and securities lending transactions, before offset, included in offsetting disclosures.

+ References

+ Details

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- Definition

Amount, before effects of master netting arrangements, of financial assets loaned to entities in exchange for collateral and funds outstanding borrowed in the form of a financial asset repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same financial assets at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

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- Definition

Amount of right to receive cash collateral under master netting arrangements that have not been offset against securities loaned.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313

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- Definition

Amount of right to receive securities collateral under master netting arrangements that have not been offset against securities loaned.

+ References

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- 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.

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