Revolving Credit Facilities, Lines Of Credit And Short-Term Borrowings (Summary Of The Borrowings Outstanding And Capacity Available Under The Facility) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2017 Parent Company [Member]
Summary of the borrowings outstanding and capacity available under the facility
Capacity	$ 3,500
Borrowings	570.0
Letters of Credit	8
Capacity Available	2,922
Capacity Decreases		$ 3,490

Revolving Credit Facilities, Lines Of Credit And Short-Term Borrowings (Summary Of The Borrowings Outstanding And Capacity Available Under The Facility) (Details) (USD $)
In Millions, unless otherwise specified

Mar. 31, 2013

Mar. 31, 2017

Parent Company [Member]

Summary of the borrowings outstanding and capacity available under the facility

$ 3,500

570.0

2,922

$ 3,490