Financial Instruments (Tables)

12 Months Ended

Mar. 31, 2017

Fair Value Disclosures [Abstract]

Carrying Amounts and Estimated Fair Values of Current and Long-Term Debt

The following table presents carrying amounts and estimated fair values of current and long-term debt:

	Carrying amount at March 31, 2017		Estimated Fair Value Using Input Type
			Quoted prices in active markets		Observable		Unobservable		Total estimated fair value
	(in millions)
Current and long-term debt	$	40,581	$	33,196	$	4,352	$	5,468	$	43,016

	Carrying amount at March 31, 2016		Estimated Fair Value Using Input Type
			Quoted prices in active markets		Observable		Unobservable		Total estimated fair value
	(in millions)
Current and long-term debt	$	33,645	$	21,757	$	4,474	$	2,130	$	28,361