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Fair Value Measurements (Carrying Values and Estimated Fair Values of Financial Liabilities) (Details) - USD ($) $ in Thousands		Mar. 31, 2020		Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term Debt		$ 302,000		$ 0
Short-term Debt, Fair Value		252,141		0
Finance lease liabilities		622		737
Long-term debt		550,577		550,597
Long-term debt, fair value		612,020		659,272
Unamortized debt issuance costs		(3,618)
Seven Point Twenty Five Percent Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		61,134		66,365
Unamortized debt issuance costs		(180)
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		49,911		49,910
Six Point Seventy Percent Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		118,561		123,104
Unamortized debt issuance costs		(346)
Six Point Seventy Percent Senior Notes [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt		99,485		99,480
Five Point Three Hundred Seventy Five Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		316,400		357,025
Unamortized debt issuance costs		(3,092)
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		294,177		294,157
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, fair value		25,261		24,901
Unamortized debt issuance costs		0
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, fair value		25,260		24,875
Unamortized debt issuance costs		0
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, fair value		65,404		63,002
Unamortized debt issuance costs		0
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		553,573		553,547
Unamortized Debt Issuance Costs [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unamortized debt issuance costs		(3,618)		(3,687)
Zero Point Seventy Eight Percent Borrowing from FHLBNY Due September 14, 2020. [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term Debt		100,000		0
Short-term Debt, Fair Value		100,096		0
Unamortized debt issuance costs		0
Zero Point Seventy Eight Percent Borrowing from FHLBNY Due September 14, 2020. [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term Debt		100,000
Zero Point Sixty Eight Percent Borrowing from FHLBNY Due September 18, 2020. [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term Debt		85,000		0
Short-term Debt, Fair Value		85,039		0
Unamortized debt issuance costs		0
Zero Point Sixty Eight Percent Borrowing from FHLBNY Due September 18, 2020. [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term Debt		85,000
Zero Point Fifty Eight Percent Borrowing from FHLBI Due December 14, 2020. [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term Debt		67,000		0
Short-term Debt, Fair Value		67,006		0
Unamortized debt issuance costs		0
Zero Point Fifty Eight Percent Borrowing from FHLBI Due December 14, 2020. [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term Debt		67,000
Two Point Two Hundred and Fourty Four Percent Borrowing from Bank of Montreal Due September 24, 2020 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term Debt		50,000	[1]	0
Short-term Debt, Fair Value		0		0
Unamortized debt issuance costs		0
Two Point Two Hundred and Fourty Four Percent Borrowing from Bank of Montreal Due September 24, 2020 [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term Debt	[1]	50,000
Short-term Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term Debt		302,000		$ 0
Unamortized debt issuance costs		0
Short-term Debt [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term Debt		$ 302,000
[1] Total short-term debt includes our $50 million line of credit borrowing. As there is no scheduled or definitive repayment plan for this borrowing as of March 31, 2020, the fair value cannot be calculated and the borrowing is not classified in the fair value hierarchy table below.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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