CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	3 Months Ended								6 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating revenues
Contract drilling revenues										$ 3,705	$ 6,802	$ 8,963
Other revenues										456	584	222
Total operating revenues	$ 974	$ 906	$ 940	$ 1,341	$ 1,851	$ 1,608	$ 1,884	$ 2,043		4,161	7,386	9,185
Costs and expenses
Operating and maintenance										1,875	2,955	5,100
Depreciation										893	963	1,129
General and administrative										172	192	234
Total costs and expenses										2,940	4,110	6,463
Loss on impairment										(93)	(1,875)	(4,043)
Gain (loss) on disposal of assets, net										4	(36)	(26)
Operating income (loss)	316	229	163	424	742	457	493	(327)		1,132	1,365	(1,347)
Other income (expense), net
Interest income										20	22	20
Interest expense, net of amounts capitalized										(409)	(432)	(483)
Gain (loss) on retirement of debt		110	38						$ 23	148	23	(13)
Other, net										43	37	35
Total other income (expense), net										(198)	(350)	(441)
Income (loss) from continuing operations before income tax expense										934	1,015	(1,788)
Income tax expense										107	120	92
Income (loss) from continuing operations	257	236	92	242	622	392	340	(459)		827	895	(1,880)
Income (loss) from discontinued operations, net of tax											2	(20)
Net income (loss)	257	236	93	241	622	395	341	(461)		827	897	(1,900)
Net income (loss) attributable to noncontrolling interest										49	32	(61)
Net income (loss) attributable to controlling interest	$ 243	$ 218	$ 82	$ 235	$ 616	$ 386	$ 335	$ (472)		$ 778	$ 865	$ (1,839)
Earnings (loss) per share-basic
Earnings (loss) from continuing operations (in dollars per share)										$ 2.08	$ 2.36	$ (5.02)
Earnings (loss) from discontinued operations (in dollars per share)												(0.06)
Earnings (loss) per share (in dollars per share)	$ 0.64	$ 0.59	$ 0.22	$ 0.64	$ 1.68	$ 1.06	$ 0.91	$ (1.30)		2.08	2.36	(5.08)
Earnings (loss) per share-diluted
Earnings (loss) from continuing operations (in dollars per share)										2.08	2.36	(5.02)
Earnings (loss) from discontinued operations (in dollars per share)												(0.06)
Earnings (loss) per share (in dollars per share)	$ 0.64	$ 0.59	$ 0.22	$ 0.64	$ 1.68	$ 1.06	$ 0.91	$ (1.30)		$ 2.08	$ 2.36	$ (5.08)
Weighted-average shares outstanding
Basic (in shares)	371	365	365	364	364	364	363	363		367	363	362
Diluted (in shares)	371	365	365	364	364	364	363	363		367	363	362