CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net income	$ 593,519	$ 743,499	$ 379,195
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	406,335	391,585	354,620
Impairment charges	20,240	0	264,256
Noncash contribution of preferred stock, net of tax	12,600	0	0
Equity in net earnings from investments	(159,278)	(139,690)	(125,300)
Distributions received from unconsolidated affiliates	167,372	144,673	122,003
Deferred income taxes	437,917	211,638	137,737
Share-based compensation expense	26,262	40,563	16,435
Pension and postretirement benefit expense, net of contributions	4,079	11,643	14,814
Allowance for equity funds used during construction	(107)	(209)	(2,179)
Gain on sale of assets	(924)	(9,635)	(5,629)
Changes in assets and liabilities:
Accounts receivable	(330,521)	(285,806)	157,051
Natural gas and natural gas liquids in storage	(202,259)	(11,950)	6,050
Accounts payable	261,305	287,632	(205,143)
Commodity imbalances, net	43,699	45,971	(4,083)
Settlement of exit activities liabilities	(9,707)	(19,906)	(38,536)
Accrued interest	22,795	(16,529)	24,166
Risk-management assets and liabilities	37,617	(78,136)	(32,370)
Other assets and liabilities, net	(15,532)	37,998	(40,259)
Cash provided by operating activities	1,315,412	1,353,341	1,022,828
Investing activities
Capital expenditures (less allowance for equity funds used during construction)	(512,393)	(624,634)	(1,188,312)
Contributions to unconsolidated affiliates	(87,861)	(68,275)	(27,540)
Distributions received from unconsolidated affiliates in excess of cumulative earnings	28,742	52,044	33,915
Proceeds from sale of assets	3,879	25,420	3,825
Other	0	0	(12,607)
Cash used in investing activities	(567,633)	(615,445)	(1,190,719)
Financing activities
Dividends paid	(829,414)	(517,601)	(509,197)
Distributions to noncontrolling interests	(276,260)	(549,419)	(535,825)
Borrowing (repayment) of short-term borrowings, net	(495,604)	563,937	(508,956)
Issuance of long-term debt, net of discounts	1,190,496	1,000,000	1,291,506
Debt financing costs	(11,425)	(2,770)	(17,515)
Repayment of long-term debt	(994,776)	(1,108,040)	(7,753)
Issuance of common stock	471,358	21,971	20,669
Issuance of common units, net of issuance costs	0	0	375,660
Other	(13,836)	5,403	(15,848)
Cash provided (used in) by financing activities	(959,461)	(586,519)	92,741
Change in cash and cash equivalents	(211,682)	151,377	(75,150)
Change in cash and cash equivalents included in discontinued operations	0	(121)	(43)
Change in cash and cash equivalents from continuing operations	(211,682)	151,256	(75,193)
Cash and cash equivalents at beginning of period	248,875	97,619	172,812
Cash and cash equivalents at end of period	37,193	248,875	97,619
Supplemental cash flow information:
Cash paid for interest, net of amounts capitalized	432,210	461,208	367,835
Cash paid for income taxes	$ 6,633	$ 361	$ 3,324