Earnings Per Share Information about Share Repurchase Plan (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015	May 10, 2012
Earnings Per Share [Abstract]
Stock Repurchase Program, Authorized Amount	$ 1,000,000			$ 1,000,000
Stock Repurchased and Retired During Period, Shares	11,697	4,537	6,931
Stock Repurchased and Retired During Period, Value	$ 381,672	$ 209,632	$ 356,522
Repurchased And Retired Shares Excluded From Weighted Average Shares Outstanding	6,005	2,564	3,528