Basis of Presentation and Significant Events - Narrative (Details)		6 Months Ended
	Jul. 02, 2015 USD ($) shares	Jun. 30, 2015 Segment
Subsequent Event [Line Items]
Number of reportable segments | Segment		3
Agreement and Plan of Merger with Aetna Inc. | Subsequent Event
Subsequent Event [Line Items]
Number of shares one share of common stock is converted into | shares	0.8375
Cash received for each share converted	$ 125
Total transaction cost, including assumption of debt	$ 37,000,000,000