Acquisitions - Additional Information (Detail) - Concentra Inc. - USD ($) $ in Millions		3 Months Ended
Jun. 01, 2015	Mar. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Selling price in cash	$ 1,055
Disposal transaction costs	$ 22
Gain on sale of business		$ 270
Revenues		246
Pretax earnings		$ 7

Amount before tax of income (loss) from a discontinued operation. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

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Amount of other expense attributable to disposal group, including, but not limited to, discontinued operation.

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Amount of revenue attributable to disposal group, including, but not limited to, discontinued operation.

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Gain (loss) from sale or disposal of an organization or integrated set of activities (for example, but not limited to, a partnership or corporation) engaged in providing a product or service in a commercial, industrial, or professional environment.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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