EQUITY COMPENSATION PLANS AND SHARE-BASED COMPENSATION, Restricted Stock Unit Activity (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Restricted Stock Units (RSUs) [Member]
Restricted Stock Units Activity, Weighted Average Grant Date Fair Value [Roll Forward]
Total intrinsic value		$ 10.0	$ 8.3	$ 15.3
Total grant date fair value		$ 9.1	$ 7.5	$ 8.6
Time Based Restricted Stock Units [Member]
Restricted Stock Unit Activity, Number of Shares [Roll Forward]
Unvested, beginning of period (in shares)		535,000	524,000	679,000
Granted (in shares)		241,000	207,000	188,000
Vested (in shares)	[1]	(151,000)	(156,000)	(288,000)
Canceled and forfeited (in shares)		(6,000)	(40,000)	(55,000)
Unvested, end of period (in shares)		619,000	535,000	524,000
Restricted Stock Units Activity, Weighted Average Grant Date Fair Value [Roll Forward]
Unvested, beginning of period (in dollars per share)	[2]	$ 46.62	$ 36.08	$ 36.08
Granted (in dollars per share)	[2]	46.41	46.05	52.90
Vested (in dollars per share)	[1],[2]	43.44	41.57	30.06
Canceled and forfeited (in dollars per share)	[2]	46.99	47.02	36.48
Unvested, end of period (in dollars per share)	[2]	$ 47.31	$ 46.62	$ 36.08
Performance Based Restricted Stock Units [Member]
Restricted Stock Unit Activity, Number of Shares [Roll Forward]
Unvested, beginning of period (in shares)		439,000	311,000	148,000
Granted (in shares)		137,000	152,000	187,000
Vested (in shares)	[1]	(62,000)	(24,000)	0
Canceled and forfeited (in shares)		0	0	(24,000)
Unvested, end of period (in shares)		514,000	439,000	311,000
Restricted Stock Units Activity, Weighted Average Grant Date Fair Value [Roll Forward]
Unvested, beginning of period (in dollars per share)	[2]	$ 47.40	$ 40.82	$ 40.82
Granted (in dollars per share)	[2]	45.84	44.54	55.08
Vested (in dollars per share)	[1],[2]	40.82	40.82	0
Canceled and forfeited (in dollars per share)	[2]	0	0	55.08
Unvested, end of period (in dollars per share)	[2]	$ 47.78	$ 47.40	$ 40.82

[1] The number of restricted stock units vested includes shares that we withheld on behalf of our employees to satisfy the statutory tax withholding requirements.

[2] The weighted average grant date fair value of restricted stock units is based on the number of shares and the closing market price of our common stock on the date of grant.