Segment Information (Long-Lived Assets By Geographic Area) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Mar. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 453	$ 434
North America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	376	369
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 77	$ 65