CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net income (loss)	$ 827	$ 897	$ (1,900)
Adjustments to reconcile to net cash provided by operating activities:
Depreciation	893	963	1,129
Share-based compensation expense	42	64	98
Loss on impairment	93	1,875	4,043
(Gain) loss on disposal of assets, net	(4)	35	36
Gain (loss) on retirement of debt	(148)	(23)	13
Deferred tax expense (benefit)	68	(134)	(194)
Other, net	14	74	24
Changes in deferred revenues, net	219	(90)	95
Changes in deferred costs, net	72	179	(49)
Changes in operating assets and liabilities	(165)	(395)	(1,075)
Net cash provided by operating activities	1,911	3,445	2,220
Cash flows from investing activities
Capital expenditures	(1,344)	(2,001)	(2,165)
Proceeds from disposal of assets, net	30	54	250
Proceeds from repayment of loans receivable		15	101
Investment in loans receivable			(15)
Other, net	1		1
Net cash used in investing activities	(1,313)	(1,932)	(1,828)
Cash flows from financing activities
Proceeds from issuance of debt, net of discounts and issue costs	2,401
Repayments of debt	(2,295)	(1,506)	(539)
Deposits to cash accounts restricted for financing activities	(85)		(20)
Proceeds from cash accounts and investments restricted for financing activities	124	110	176
Proceeds from sale of noncontrolling interest, net of issue costs			417
Distributions of qualifying additional paid-in capital		(381)	(1,018)
Distribution to holders of noncontrolling interest	(30)	(29)	(5)
Other, net		(3)	(11)
Net cash provided by (used in) financing activities	115	(1,809)	(1,000)
Net increase (decrease) in cash and cash equivalents	713	(296)	(608)
Cash and cash equivalents at beginning of period	2,339	2,635	3,243
Cash and cash equivalents at end of period	$ 3,052	$ 2,339	$ 2,635