Business Acquisitions - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended	11 Months Ended
Nov. 01, 2017	Sep. 30, 2018	Sep. 30, 2018
Business Acquisition [Line Items]
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Total Assets		$ 80	$ 80
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Total Liabilities		80	$ 80
Goodwill, Purchase Accounting Adjustments		$ 0
Aetna Group Insurance
Business Acquisition [Line Items]
Total	$ 1,452

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Total Assets

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- Definition

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Total Liabilities

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- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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