Credit Facility Covenant on Maximum Ratio of Indebtedness

No definition available.

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- Definition

Line of Credit Facility, Maximum Number Of Institutions Participating In The Facility Pertaining to Maximum Contributory Percentage

+ References

No definition available.

+ Details

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- Definition

Line of Credit Facility, Maximum Percentage of Total Availability Provided by a Single Lender

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Line of Credit Facility, Number of Institutions Participating in the Facility

+ References

No definition available.

+ Details

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- Definition

Maximum Ratio Of Indebtedness To Net Capital Threshold Percentage

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Short Term Debt Basis Spread On Variable Rate

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ 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

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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

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Maturity date of long-term debt, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	instant

- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ 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(19)(a))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: 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(a)(16)(a)(1))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

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-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Financing Activities (Details) $ in Thousands	3 Months Ended	9 Months Ended
Financing Activities (Details) $ in Thousands	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($) banks	Dec. 31, 2019 USD ($)
Short-term Debt [Line Items]
Short term borrowings	$ 100,000	$ 100,000	$ 0
Unsecured Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 425,000	$ 425,000
Line of Credit Facility, Expiration Date		Sep. 02, 2023
Line of Credit Facility, Number of Institutions Participating in the Facility \| banks		10
Line of Credit Facility, Maximum Number Of Institutions Participating In The Facility Pertaining to Maximum Contributory Percentage \| banks		1
Line of Credit Facility, Maximum Percentage of Total Availability Provided by a Single Lender	13.00%	13.00%
Credit Facility Covenant on Maximum Ratio of Indebtedness		65.00%
Unsecured Revolving Line of Credit, Additional Amount Available Under Accordion Feature [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 75,000	$ 75,000
Eurodollar [Member] \| Minimum [Member] \| Unsecured Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		112.50%
Eurodollar [Member] \| Maximum [Member] \| Unsecured Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		175.00%
Base Rate [Member] \| Minimum [Member] \| Unsecured Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		12.50%
Base Rate [Member] \| Maximum [Member] \| Unsecured Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		75.00%
Secured Debt Montana Due 2030 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 100,000	$ 100,000
Debt Instrument, Interest Rate, Stated Percentage	3.21%	3.21%
Long-term Debt, Maturity Date	May 15, 2030	May 15, 2030
Secured Debt South Dakota Due 2030 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 50,000	$ 50,000
Debt Instrument, Interest Rate, Stated Percentage	3.21%	3.21%
Long-term Debt, Maturity Date	May 15, 2030	May 15, 2030
Term Loan Due 2021 [Member]
Short-term Debt [Line Items]
Short term borrowings	$ 100,000	$ 100,000
Maximum Ratio Of Indebtedness To Net Capital Threshold Percentage	65.00%
Term Loan Due 2021 [Member] \| Eurodollar [Member]
Short-term Debt [Line Items]
Short Term Debt Basis Spread On Variable Rate	1.50%