Revenue from Contracts with Customers - Schedule of Disaggregation of Revenues (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Operating revenues and other	$ 961	$ 979	$ 1,946	$ 2,022
Total revenues from contracts with customers	945	965	1,912	1,988
Other revenues	16	14	34	34
CNA Financial [Member] \| Non-insurance Warranty [Member]
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	285	248	566	486
Diamond Offshore [Member] \| Drilling Contracts [Member]
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	216	268	450	564
Boardwalk Pipeline [Member] \| Transportation and Storage of Natural Gas and NGLs and Other Services [Member]
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	321	281	660	612
Loews Hotels And Co [Member] \| Lodging and Related Services [Member]
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	185	200	365	383
Corporate [Member] \| Rigid Plastic Packaging and Recycled Resin [Member]
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	$ 223	$ 216	$ 437	$ 429

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Amount of revenue and income classified as other.

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