Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenues	$ 3,761	$ 3,343
Costs and expenses:
Operating	2,400	2,074
Selling, general and administrative	524	488
Depreciation and amortization	56	55
Merger and acquisition-related costs	9	0
Total costs and expenses	2,989	2,617
Operating income (loss)	772	726
Interest expense	(118)	(109)
Interest income	17	13
Other items, net	(11)	(21)
Earnings (loss) before income taxes and equity in earnings (loss) of investee companies	660	609
Provision for income taxes	(135)	(138)
Equity in loss of investee companies, net of tax	(14)	(17)
Net earnings from continuing operations	511	454
Net loss from discontinued operations, net of tax	0	(706)
Net earnings (loss)	$ 511	$ (252)
Basic net earnings (loss) per common share:
Basic net earnings from continuing operations (in dollars per share)	$ 1.34	$ 1.11
Basic net loss from discontinued operations (in dollars per share)	0.00	(1.72)
Basic net earnings (loss) (in dollars per share)	1.34	(0.61)
Diluted net earnings (loss) per common share:
Diluted net earnings from continuing operations (in dollars per share)	1.32	1.09
Diluted net loss from discontinued operations (in dollars per share)	0.00	(1.70)
Diluted net earnings (loss) (in dollars per share)	$ 1.32	$ (0.61)
Weighted average number of common shares outstanding:
Basic (in shares)	382	410
Diluted (in shares)	386	416
Dividends per common share (in dollars per share)	$ 0.18	$ 0.18