Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenues	$ 3,295	$ 3,263	$ 11,271	$ 10,490
Costs and expenses:
Operating	2,078	1,922	7,335	6,506
Selling, general and administrative	584	549	1,702	1,605
Depreciation and amortization	52	56	158	168
Restructuring charges	0	0	108	25
Merger-related costs and other corporate matters	80	46	93	65
Gain on sale of assets	0	0	(549)	0
Total costs and expenses	2,794	2,573	8,847	8,369
Operating income (loss)	501	690	2,424	2,121
Interest expense	(114)	(115)	(346)	(349)
Interest income	12	12	38	43
Other items, net	(24)	(17)	(66)	(52)
Earnings (loss) before income taxes and equity in earnings (loss) of investee companies	375	570	2,050	1,763
(Provision) benefit for income taxes	(33)	(64)	344	(312)
Equity in loss of investee companies, net of tax	(23)	(18)	(52)	(52)
Net earnings	$ 319	$ 488	$ 2,342	$ 1,399
Basic net earnings per common share (in dollars per share)	$ 0.85	$ 1.30	$ 6.26	$ 3.70
Diluted net earnings per common share (in dollars per share)	$ 0.85	$ 1.29	$ 6.23	$ 3.66
Weighted average number of common shares outstanding:
Basic (in shares)	374	375	374	378
Diluted (in shares)	376	379	376	382