EQUITY COMPENSATION PLANS AND SHARE-BASED COMPENSATION, Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Apr. 30, 2015	Apr. 30, 2014
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total intrinsic value		$ 3.5	$ 3.4	$ 14.1	$ 11.1
Total grant date fair value		1.9	$ 1.7	7.9	$ 7.1
Time-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense		$ 20.0		$ 20.0
Weighted average service period for recognition of unrecognized compensation costs				2 years 3 months 18 days
Restricted Stock Unit Activity, Number of Shares [Roll Forward]
Nonvested, beginning of period (in shares)				679,000
Granted (in shares)				186,000
Vested (in shares)	[1]			(264,000)
Canceled and forfeited (in shares)				(47,000)
Nonvested, end of period (in shares)		554,000		554,000
Restricted Stock Units Activity, Weighted Average Grant Date Fair Value [Roll Forward]
Nonvested, beginning of period (in dollars per share)	[2]			$ 36.08
Granted (in dollars per share)	[2]			52.95
Vested (in dollars per share)	[1],[2]			30.04
Canceled and forfeited (in dollars per share)	[2]			35.00
Nonvested, end of period (in dollars per share)	[2]	$ 44.73		$ 44.73
Time-Based Restricted Stock Units [Member] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time-based vesting schedules				Four-year time-based vesting as follows: five percent vesting after the first year; additional ten percent after the second year; additional 15 percent after the third year; and the remaining 70 percent after the fourth year of continuous employment with the Company.
Vesting percentage after first year				5.00%
Additional vesting percentage after second year				10.00%
Additional vesting percentage after third year				15.00%
Additional vesting percentage after fourth year				70.00%
Time-Based Restricted Stock Units [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time-based vesting schedules				100 percent vesting after one year of continuous service to the Company.
Vesting percentage after first year				100.00%
Performance-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense		$ 9.7		$ 9.7
Weighted average service period for recognition of unrecognized compensation costs				2 years 6 months
Restricted Stock Unit Activity, Number of Shares [Roll Forward]
Nonvested, beginning of period (in shares)				148,000
Granted (in shares)				187,000
Vested (in shares)	[1]			0
Canceled and forfeited (in shares)				(24,000)
Nonvested, end of period (in shares)		311,000		311,000
Restricted Stock Units Activity, Weighted Average Grant Date Fair Value [Roll Forward]
Nonvested, beginning of period (in dollars per share)	[2]			$ 40.82
Granted (in dollars per share)	[2]			55.08
Vested (in dollars per share)	[1],[2]			0
Canceled and forfeited (in dollars per share)	[2]			55.08
Nonvested, end of period (in dollars per share)	[2]	$ 48.29		$ 48.29
FY 2015 Performance RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Approved restricted stock unit awards (performance vesting) (in shares)							172,000
FY 2015 Performance RSUs [Member] | Target Condition One [Member]
Performance target of restricted stock units by vesting date [Abstract]
Shares Issuable Upon Settlement				25.00%
Consolidated Income from Operations				> 90% of target
Vesting Date				Third anniversary of the date of grant
FY 2015 Performance RSUs [Member] | Target Condition Two [Member]
Performance target of restricted stock units by vesting date [Abstract]
Shares Issuable Upon Settlement				25.00%
Consolidated Income from Operations				> 90% of target
Vesting Date				Fourth anniversary of the date of grant
FY 2015 Performance RSUs [Member] | Target Condition Three [Member]
Performance target of restricted stock units by vesting date [Abstract]
Shares Issuable Upon Settlement				25.00%
Consolidated Income from Operations				>100% of target
Vesting Date				Third anniversary of the date of grant
FY 2015 Performance RSUs [Member] | Target Condition Four [Member]
Performance target of restricted stock units by vesting date [Abstract]
Shares Issuable Upon Settlement				25.00%
Consolidated Income from Operations				> 100% of target
Vesting Date				Fourth anniversary of the date of grant
FY 2016 Performance RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Approved restricted stock unit awards (performance vesting) (in shares)						187,000
FY 2016 Performance RSUs [Member] | Target Condition One [Member]
Performance target of restricted stock units by vesting date [Abstract]
Shares Issuable Upon Settlement				25.00%
Consolidated Income from Operations				> 90% of target
Vesting Date				Third anniversary of the date of grant
FY 2016 Performance RSUs [Member] | Target Condition Two [Member]
Performance target of restricted stock units by vesting date [Abstract]
Shares Issuable Upon Settlement				25.00%
Consolidated Income from Operations				> 90% of target
Vesting Date				Fourth anniversary of the date of grant
FY 2016 Performance RSUs [Member] | Target Condition Three [Member]
Performance target of restricted stock units by vesting date [Abstract]
Shares Issuable Upon Settlement				25.00%
Consolidated Income from Operations				>100% of target
Vesting Date				Third anniversary of the date of grant
FY 2016 Performance RSUs [Member] | Target Condition Four [Member]
Performance target of restricted stock units by vesting date [Abstract]
Shares Issuable Upon Settlement				25.00%
Consolidated Income from Operations				> 100% of target
Vesting Date				Fourth anniversary of the date of grant

[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.