CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ (400,314)	$ 100,066	$ (11,792)
Adjustments to reconcile net income to net cash provided by operating activities -
Depreciation, depletion and amortization	295,322	319,806	313,190
Loss (gain) on sale of assets	22,045	0	(42,264)
Impairment expense	280,826	0	126,282
Amortization and write-off of debt issuance costs and premium or discount	22,610	10,766	12,165
Amortization of unearned income and initial direct costs on direct financing leases	(8,847)	(12,247)	(13,035)
Payments received under direct financing leases	56,837	20,668	20,668
Equity in earnings of investments in equity investees	(64,019)	(56,484)	(43,626)
Cash distributions of earnings of equity investees	63,721	56,081	42,735
Non-cash effect of long-term incentive compensation plans	(3,693)	8,496	3,941
Deferred and other tax benefits	512	65	663
Cancellation of debt income	(27,302)	0	0
Unrealized (gains) losses on derivative transactions	1,191	12,586	(11,795)
Other, net	19,229	(6,418)	(4,941)
Net changes in components of operating assets and liabilities	38,627	(71,098)	(2,152)
Net cash provided by operating activities	296,745	382,287	390,039
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments to acquire fixed and intangible assets	(144,133)	(163,248)	(195,367)
Cash distributions received from equity investees—return of investment	17,340	21,250	28,979
Investments in equity investees	0	0	(3,018)
Proceeds from asset sales	23,037	1,187	310,099
Net cash used in (provided by) investing activities	(103,756)	(140,811)	140,693
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings on senior secured credit facility	1,023,000	815,100	980,700
Repayments on senior secured credit facility	(1,338,600)	(825,900)	(1,109,800)
Proceeds from issuance of senior unsecured notes (Note 10)	1,500,000	0	0
Net proceeds from issuance of preferred units (Note 11)	0	122,900	0
Repayment of senior unsecured notes (Note 10)	(1,185,096)	0	(145,170)
Debt issuance costs	(26,680)	0	(242)
Contributions from noncontrolling interests	2,354	5,652	2,592
Distributions to Class A Convertible Preferred unitholders (Note 11)	(74,736)	(43,506)	0
Distributions to common unitholders (Note 11)	(122,580)	(269,674)	(257,416)
Other, net	(38)	57	(137)
Net cash provided used in financing activities	(222,376)	(195,371)	(529,473)
Net increase (decrease) in cash and cash equivalents and restricted cash	(29,387)	46,105	1,259
Cash and cash equivalents and restricted cash at beginning of period	56,405	10,300	9,041
Cash and cash equivalents and restricted cash at end of period	$ 27,018	$ 56,405	$ 10,300