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Fair Value Measurements (Carrying Values and Estimated Fair Values of Financial Liabilities) (Details) - USD ($) $ in Thousands | Jun. 30, 2019 | Jan. 01, 2019 | Dec. 31, 2018
--- | --- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Finance lease liabilities | $ 1,109 | [1] | $ 900 | $ 0 | [1]
Long-term Debt | 550,778 |  |  |  |
Long-term Debt |  |  |  | 439,540 |
Long-term debt, fair value | 623,655 |  |  | 448,622 |
Seven Point Twenty Five Percent Senior Notes [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 49,713 |  |  |  |
Long-term Debt |  |  |  | 49,700 |
Long-term debt, fair value | 63,519 |  |  | 57,032 |
Seven Point Twenty Five Percent Senior Notes [Member] | Reported Value Measurement [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 49,909 |  |  | 49,907 |
Six Point Seventy Percent Senior Notes [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 99,097 |  |  |  |
Long-term Debt |  |  |  | 99,069 |
Long-term debt, fair value | 118,482 |  |  | 107,075 |
Six Point Seventy Percent Senior Notes [Member] | Reported Value Measurement [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 99,471 |  |  | 99,462 |
Five Point Eight Hundred Seventy Five Senior Notes [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 0 |  |  |  |
Long-term Debt |  |  |  | 180,771 |
Long-term debt, fair value | 0 |  |  | 177,230 |
Five Point Eight Hundred Seventy Five Senior Notes [Member] | Reported Value Measurement [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 0 |  |  | 185,000 |
Five Point Three Hundred Seventy Five Senior Notes [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 290,859 |  |  |  |
Long-term Debt |  |  |  | 0 |
Long-term debt, fair value | 329,785 |  |  | 0 |
Five Point Three Hundred Seventy Five Senior Notes [Member] | Reported Value Measurement [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 294,116 |  |  | 0 |
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 25,000 |  |  |  |
Long-term Debt |  |  |  | 25,000 |
Long-term debt, fair value | 24,756 |  |  | 24,218 |
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member] | Reported Value Measurement [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 25,000 |  |  | 25,000 |
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 25,000 |  |  |  |
Long-term Debt |  |  |  | 25,000 |
Long-term debt, fair value | 24,720 |  |  | 24,162 |
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member] | Reported Value Measurement [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 25,000 |  |  | 25,000 |
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 60,000 |  |  |  |
Long-term Debt |  |  |  | 60,000 |
Long-term debt, fair value | 62,393 |  |  | 58,905 |
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member] | Reported Value Measurement [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 60,000 |  |  | 60,000 |
Long Term Debt Excluding Issuance Costs and Finance Lease Obligations [Member] | Reported Value Measurement [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Long-term Debt | 553,496 |  |  | 444,369 |
Unamortized Debt Issuance Costs [Member] | Reported Value Measurement [Member] |  |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |  |
Unamortized debt issuance costs | $ (3,827) |  |  | $ (4,829) |
[1] | Concurrent with the adoption of ASU 2016-02 discussed in Note 2. "Adoption of Accounting Pronouncements," finance lease obligations are now captured in Long-term debt on our Consolidated Balance Sheets.

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- Definition Amount, after unamortized (discount) premium of long-term debt. + References No definition available. + Details
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- Definition Present value of lessee's discounted obligation for lease payments from finance lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918701-209980 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977 + Details
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- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870 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)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -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 Reference 4: 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)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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