Equity Incentive Plans, Share-based Payment Award (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
RSU nonvested shares beginning balance	5,268,916	5,530,034	6,009,831
RSU shares granted	2,479,729	1,446,968	1,616,632
RSU shares assumed upon acquisition	525,442
RSU shares forfeited/expired	(360,072)	(266,415)	(282,964)
RSU shares vested	(1,606,273)	(1,441,671)	(1,813,465)
RSU nonvested shares ending balance	6,307,742	5,268,916	5,530,034
Closing price of company's common stock related to calculation of aggregate intrinsic value of stock options (in dollars per share)	$ 48.20
Restricted stock units' weighted average remaining expense recognition period (in years)	2 years 3 months 20 days
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Total intrinsic value of RSU's vested during the period	$ 72.1	$ 67.6	$ 74.6
Total intrinsic value of RSU's outstanding	$ 304.0
Restricted stock units' weighted average remaining expense recognition period (in years)	2 years 4 months 6 days
Weighted average fair values per share of restricted stock units awarded (amount per share)	$ 38.92	$ 42.02	$ 34.24