Stockholders' Equity 3 (Details) - USD ($) $ in Millions	Sep. 30, 2018	Mar. 31, 2018
Accumulated Other Comprehensive Loss
Accumulated other comprehensive loss
Foreign currency translation losses	$ (463)	$ (290)

Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses.

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Data Type:	xbrli:monetaryItemType
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