Consolidated Statments of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net income	$ 869,531		$ 802,771	$ 819,122
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	196,630		178,142	166,812
Loss (gain) on sale and retirement of assets	(5,135)		11,190	7,871
Earnings of non-controlled entities	(120,994)		(78,696)	(66,483)
Distributions from investments in non-controlled entities	123,660		78,723	66,285
Equity-based incentive compensation expense	20,641		19,358	24,245
Settlement cost, amortization of prior service credit and actuarial loss	8,650		2,211	3,478
Gain on exchange of interest in non-controlled entity	0		(28,144)	0
Changes in components of operating assets and liabilities (Note 3)	15,695		(21,515)	48,362
Net cash provided by operating activities	1,108,678		964,040	1,069,692
Investing Activities:
Additions to property, plant and equipment	(558,669)		(674,159)	(621,151)
Proceeds from sale and disposition of assets	44,392		7,552	3,371
Acquisition of business	0		0	(54,678)
Investments in non-controlled entities	(134,828)		(200,023)	(152,466)
Distributions in excess of earnings of non-controlled entities	78,482	[1]	9,264	14,155
Net cash used by investing activities	(570,623)		(857,366)	(810,769)
Financing Activities:
Distributions paid	(803,216)		(739,157)	(662,948)
Net commercial paper repayments	(49,986)		(229,975)	(16,981)
Borrowings under long-term notes	496,705		1,142,997	499,589
Payments on notes	0		(250,000)	0
Debt placement costs	(6,316)		(10,906)	(6,223)
Net payment on financial derivatives	0		(19,287)	(42,908)
Payments associated with settlement of equity-based incentive compensation	(13,875)		(14,376)	(17,784)
Net cash used by financing activities	(376,688)		(120,704)	(247,255)
Change in cash and cash equivalents	161,367		(14,030)	11,668
Cash and cash equivalents at beginning of period	14,701		28,731	17,063
Cash and cash equivalents at end of period	176,068		14,701	28,731
Noncash Investing and Financing Items [Abstract]
Contribution of property, plant and equipment to a non-controlled entity	97,638		0	13,252
Issuance of limited partner units in settlement of equity-based incentive plan awards	1,669		7,289	8,045
Additions to property, plant and equipment	(572,744)		(653,528)	(623,289)
Changes in accounts payable and other current liabilities related to capital expenditures	14,075		(20,631)	2,138
Additions to property, plant and equipment, net	$ (558,669)		$ (674,159)	$ (621,151)

[1] Includes the $48.8 million distribution to us from MVP as reimbursement for the PP&E we contributed, as well as an additional distribution of $6.2 million from BridgeTex that is not related to the ongoing operations of non-controlled entities.