Proposed Acquisition of Aetna (Details) - Aetna $ / shares in Units, item in Millions, $ in Billions	Dec. 03, 2017 USD ($) $ / shares shares	Oct. 10, 2018 item
Business Acquisition
Cash consideration for shares acquired (dollars per share) | $ / shares	$ 145.00
Shares exchanged for each share acquired (in shares) | shares	0.8378
The assigned value per share of acquiree (dollars per share) | $ / shares	$ 207
Assigned value of acquiree | $	$ 69.0
Weighted average share price analysis	5 days
Consideration transferred | $	$ 77.0
Potential termination fees | $	$ 2.1
Number of members in Medicare Part D prescription drug plan. | item		2.2
Aetna Acquisition
Business Acquisition
Share price (dollars per share) | $ / shares	$ 74.21