Debt (Tables)

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Schedule of Long-Term Debt

	December 31, 2021						December 31, 2020
	Principal Value		Carrying Value (a)		Fair Value (b)		Principal Value		Carrying Value (a)		Fair Value (b)
	(Thousands)
Credit Facility expires July 31, 2023	$	—	$	—	$	—	$	300,000	$	300,000	$	300,000
Senior notes:
8.81% to 9.00% series A notes due 2020 – 2021	—		—		—		24,000		24,000		25,232
4.875% notes due November 15, 2021	—		—		—		125,118		124,943		128,231
3.00% notes due October 1, 2022	568,823		567,909		576,969		568,823		566,689		578,055
7.42% series B notes due 2023	10,000		10,000		10,327		10,000		10,000		10,038
6.625% notes due February 1, 2025 (c)	1,000,000		994,643		1,133,000		1,000,000		992,905		1,146,250
1.75% convertible notes due May 1, 2026	499,991		381,473		854,985		500,000		359,635		587,385
3.125% notes due May 15, 2026	500,000		493,157		516,265		—		—		—
7.75% debentures due July 15, 2026	115,000		112,721		138,504		115,000		112,224		137,025
3.90% notes due October 1, 2027	1,250,000		1,243,340		1,344,688		1,250,000		1,242,182		1,249,400
5.00% notes due January 15, 2029	350,000		344,835		389,428		350,000		344,106		371,469
7.500% notes due February 1, 2030 (c)	750,000		744,417		966,983		750,000		743,726		924,510
3.625% notes due May 15, 2031	500,000		492,669		523,620		—		—		—
Note payable to EQM	99,838		99,838		117,837		105,056		105,056		130,464
Total debt	5,643,652		5,485,002		6,572,606		5,097,997		4,925,466		5,588,059
Less: Current portion of debt	1,074,332		954,900		1,439,165		154,336		154,161		159,943
Long-term debt	$	4,569,320	$	4,530,102	$	5,133,441	$	4,943,661	$	4,771,305	$	5,428,116

(a)For the Company's credit facility and note payable to EQM, the principal value represents the carrying value. For all other debt, the principal value less the unamortized debt issuance costs and debt discounts represents the carrying value.

(b)The carrying value of borrowings under the Company's credit facility approximates fair value as the interest rate is based on prevailing market rates; therefore, it is a Level 1 fair value measurement. For the Company's note payable to EQM, fair value is measured using Level 3 inputs. For all other debt, fair value is measured using Level 2 inputs. See Note 4 for a description of the fair value hierarchy.

(c)Interest rates for the Adjustable Rate Notes (defined below) are as of December 31, 2021. For the notes due February 1, 2025 and the notes due February 1, 2030, the interest rates were 7.875% and 8.750%, respectively, as of December 31, 2020.

Convertible Debt

The table below summarizes the net carrying amount of the Convertible Notes, including the unamortized debt discount and debt issuance costs.

	December 31,
	2021		2020
	(Thousands)
Principal	$	499,991	$	500,000
Less: Unamortized debt discount	108,719		129,102
Less: Unamortized debt issuance costs	9,799		11,263
Net carrying value of Convertible Notes	$	381,473	$	359,635

The table below summarizes the components of interest expense related to the Convertible Notes.

	Years Ended December 31,
	2021		2020
	(Thousands)
Contractual interest expense	$	8,750	$	5,906
Amortization of debt discount	20,382		12,856
Amortization of issuance costs	1,464		853
Total Convertible Notes interest expense	$	30,596	$	19,615