CONSOLIDATED CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Statement of Cash Flows [Abstract]
Cash flows provided by operating activities	$ 404	$ 203
Cash flows from investing activities
Acquisitions of property and equipment, net of change in related payables	(215)	(164)
Proceeds from the sale and maturity of investments	28	26
Payments to acquire investments	(16)	(18)
Cash flows used in investing activities	(203)	(156)
Cash flows from financing activities
Proceeds from long-term debt and revolving credit	467	285
Debt issuance costs and fees	5	8
Repayments of long-term debt and revolving credit facilities	(500)	(348)
Proceeds from the issuance of common stock	4	7
Repurchase of common stock	31	0
Payments Related to Tax Withholding for Share-based Compensation	(12)	(9)
Repayments of Other Debt	(5)	0
Proceeds from Noncontrolling Interests	20	0
Distributions to noncontrolling interest owners	0	(6)
Cash flows used in financing activities	(62)	(79)
Net increase/(decrease) in cash, cash equivalents, and restricted cash	139	(32)
Cash, cash equivalents, and restricted cash, beginning of period	2,709	4,658
Cash, cash equivalents, and restricted cash, end of period	2,848	4,626
Supplemental Cash Flow Information:
Cash paid for interest	581	272
Cash paid for income taxes	4	3
Change in accrued capital expenditures	$ 10	$ (9)