Noncontrolling Interests and Redeemable Noncontrolling Interests - Narrative (Details) shares in Millions	1 Months Ended		9 Months Ended	12 Months Ended
	Jul. 31, 2014 USD ($)	Apr. 30, 2014 USD ($) shares	Dec. 31, 2015	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) € / shares	Dec. 02, 2014 € / shares
Noncontrolling Interest [Line Items]
Put right value, exercise period			2 months	2 months
Noncontrolling Interest
Noncontrolling Interest [Line Items]
Decrease in noncontrolling interest					$ 60,000,000
Celesio
Noncontrolling Interest [Line Items]
Annual recurring compensation (in euro per share) | € / shares							€ 0.83
Dividends paid (in euro per share) | € / shares						€ 0.83
Put right (in dollars per share) | € / shares							€ 22.99
Percentage points							5.00%
Total attribution of net income to the noncontrolling shareholders				$ 44,000,000	62,000,000
Carrying value of noncontrolling interests				1,410,000,000	1,390,000,000	€ 1,500,000,000
Maximum redemption value				$ 1,280,000,000.00	$ 1,210,000,000.00
Percentage of outstanding common shares				76.00%	76.00%
Celesio | Redeemable Noncontrolling Interests
Noncontrolling Interest [Line Items]
Guaranteed dividend amount					$ 50,000,000
Recurring compensation				$ 44,000,000	12,000,000
Decrease in noncontrolling interest					9,000,000
Celesio | Noncontrolling Interest
Noncontrolling Interest [Line Items]
Decrease in noncontrolling interest	$ 25,000,000	$ 35,000,000
Additional purchase of shares | shares		1
Net foreign currency translation losses attributable to noncontrolling interest					$ 138,000,000