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Indebtedness Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.03%
Long-term Debt, Gross	$ 60,000
Long-term Debt	60,000	$ 60,000
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	1.56%
Long-term Debt, Gross	$ 25,000
Long-term Debt	25,000	25,000
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	1.61%
Long-term Debt, Gross	$ 25,000
Long-term Debt	25,000	25,000
Five Point Eight Hundred Seventy Five Percent Senior Notes [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (4,570)
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	5.88%
Long-term Debt, Gross	$ 185,000
Long-term Debt	180,430	180,068
Six Point Seventy Percent Senior Notes [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (989)
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	6.70%
Long-term Debt, Gross	$ 100,000
Long-term Debt	99,011	98,952
Seven Point Twenty Five Percent Senior Notes [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (325)
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	7.25%
Long-term Debt, Gross	$ 50,000
Long-term Debt	49,675	49,647
Long-term Debt [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	(5,884)
Long-term Debt, Gross	445,000
Long-term Debt	$ 439,116	$ 438,667

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Long Term Debt Excluding Debt Discount And Debt Issuance Costs

+ References

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Amount of unamortized debt discount (premium) and debt issuance costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

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- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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=6877327&loc=d3e13212-122682

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