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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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LONG-TERM DEBT - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jan. 23, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt, gross	$ 785,000		$ 554,000
Less amounts due within one year	0		24,000
Less unamortized debt discount	360		387
Less unamortized debt issuance costs	1,779		2,170
Long-term debt	782,861		527,443
Credit facility, due August 30, 2019 \| Credit facility, due August 30, 2019
Debt Instrument [Line Items]
Long-term debt, gross	255,000		0
Medium-term Notes \| 7.40% Medium-term Notes, Series A, due July 24, 2017
Debt Instrument [Line Items]
Long-term debt, gross	$ 0	$ 2,000	2,000
Interest rate (in percentage)	7.40%	7.40%
Medium-term Notes \| 7.36% Medium-term Notes, Series A, due July 24, 2017
Debt Instrument [Line Items]
Long-term debt, gross	$ 0		15,000
Interest rate (in percentage)	7.36%
Medium-term Notes \| 7.23% Medium-term Notes, Series A, due July 28, 2017
Debt Instrument [Line Items]
Long-term debt, gross	$ 0		2,000
Interest rate (in percentage)	7.23%
Medium-term Notes \| 7.32% Medium-term Notes, Series A, due July 28, 2022
Debt Instrument [Line Items]
Long-term debt, gross	$ 20,000		20,000
Interest rate (in percentage)	7.32%
Medium-term Notes \| 7.60% Medium-term Notes, Series A, due July 26, 2027
Debt Instrument [Line Items]
Long-term debt, gross	$ 0	$ 5,000	5,000
Interest rate (in percentage)	7.60%	7.60%
Medium-term Notes \| 7.35% Medium-term Notes, Series A, due July 28, 2027
Debt Instrument [Line Items]
Long-term debt, gross	$ 10,000		10,000
Interest rate (in percentage)	7.35%
Medium-term Notes \| 7.125% Medium-term Notes, Series B, due February 15, 2028
Debt Instrument [Line Items]
Long-term debt, gross	$ 100,000		100,000
Interest rate (in percentage)	7.125%
Notes \| 4.625% Notes, due September 1, 2021
Debt Instrument [Line Items]
Long-term debt, gross	$ 400,000		$ 400,000
Interest rate (in percentage)	4.625%