Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 23,427	$ 17,489
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	14,021	24,554
Amortization expense—affiliates	722	838
Distributions from equity earnings from unconsolidated investments	12,250	10,903
Asset impairment	2,030	0
Gain on asset sales	(21,925)	(2,066)
Equity earnings from unconsolidated investment	(9,801)	(12,523)
Other, net	1,887	1,056
Other, net—affiliates	664	7
Change in operating assets and liabilities:
Accounts receivable	5,782	15,110
Accounts receivable—affiliates	(661)	3,643
Accounts payable	(48)	(2,642)
Accounts payable—affiliates	(237)	(14)
Accrued liabilities	(5,900)	(5,354)
Deferred revenue	(4,063)	5,845
Deferred revenue—affiliates	(985)	(738)
Other items, net	1,146	103
Other items, net—affiliates	1,119	(739)
Net cash provided by operating activities	19,428	55,472
Cash flows from investing activities:
Acquisition of mineral rights	(2,725)	(16,788)
Acquisition of plant and equipment and other	(2,221)	(1,365)
Proceeds from sale of plant and equipment and other	3	905
Proceeds from sale of oil and gas properties	32,848	3,395
Proceeds from sale of coal and hard mineral royalty properties	9,802	866
Return of long-term contract receivables—affiliate	309	1,137
Net cash provided by (used in) investing activities	38,016	(11,850)
Cash flows from financing activities:
Proceeds from loans	0	25,000
Repayments of loans	(51,166)	(41,166)
Distributions to partners	(5,616)	(43,678)
Distributions to non-controlling interest	0	(662)
Debt issue costs and other	(338)	83
Net cash used in financing activities	(57,120)	(60,423)
Net increase (decrease) in cash and cash equivalents	324	(16,801)
Cash and cash equivalents at beginning of period	51,773	50,076
Cash and cash equivalents at end of period	52,097	33,275
Supplemental cash flow information:
Cash paid during the period for interest	13,812	14,344
Plant, equipment and mineral rights funded with accounts payable or accrued liabilities	$ 811	$ 3,761