Debt - Senior Unsecured Notes (Details) - Senior unsecured notes - USD ($)	Mar. 17, 2020	Dec. 31, 2020
Series G and Series H senior unsecured notes
Debt Instrument [Line Items]
Face amount	$ 175,000,000
Issue price, as a percent of aggregate principal amount	100.00%
Series G
Debt Instrument [Line Items]
Face amount	$ 100,000,000
Stated interest rate (as a percent)	3.61%	3.61%
Series H
Debt Instrument [Line Items]
Face amount	$ 75,000,000
Stated interest rate (as a percent)	3.73%	3.73%

Debt Instrument, Issue Price, Percentage Of Aggregate Principal Amount

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

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-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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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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