Stockholders' Equity and Per Share Data (Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Mar. 31, 2017
Shareholders' Equity and Per Share Data [Abstract]
Unrecognized net periodic pension and postretirement benefit cost	$ (337)	$ (369)
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	8	0
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	32	(2)
Foreign currency translation adjustments	(16)	(33)
Accumulated other comprehensive loss	$ (313)	$ (404)