STOCK-BASED COMPENSATION - UNRECOGNIZED COMPENSATION EXPENSE (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2016
Stock options, number of shares
Exercised (in shares)	(2,500)	(20,488)	(34,495)
Stock Options
Key assumptions used in Black-Scholes model to determine the fair value of each stock option and SAR
Weighted-average expected volatility (as a percent)	36.90%	37.30%	43.60%
Weighted-average expected life (in years)	5 years 6 months	5 years 6 months	5 years 6 months
Weighted-average dividend yield (as a percent)	1.06%	1.00%	1.00%
Weighted-average risk free interest rate (as a percent)	1.60%	1.70%	1.70%
Stock options, number of shares
Outstanding at the beginning of the period (in shares)	96,155
Granted (in shares)	25,437
Exercised (in shares)	(2,500)
Forfeited (in shares)	(1,269)
Outstanding at the end of the period (in shares)	117,823	96,155
Exercisable at the end of the period (in shares)				73,366
Stock options, weighted-average exercise price
Outstanding at the beginning of the period (in dollars per share)	$ 59.28
Granted (in dollars per share)	55.71
Exercised (in dollars per share)	28.78
Forfeited (in dollars per share)	69.94
Outstanding at the end of the period (in dollars per share)	$ 59.04	$ 59.28
Exercisable at the end of the period (in dollars per share)				$ 57.46
Stock options, weighted-average remaining contractual life (in years)
Outstanding at the end of the period	6 years 4 months 24 days
Exercisable at the end of the period	5 years 1 month 6 days
Stock options, Aggregate Intrinsic Value
Outstanding at the end of the period				$ 1,632
Exercisable at the end of the period				1,129
Granted (in dollars per share)	$ 18.05	$ 24.86	$ 22.78
Intrinsic value of options exercised	$ 100	$ 700	$ 1,100
Unrecognized stock-based compensation expense
Unrecognized compensation expense				500
Weighted-average vesting period (years)	1 year 8 months 12 days
Contractual term of awards	10 years
Stock Options | Minimum
Stock Options and Stock Appreciation Rights
Continuous service period for awards to vest	1 year
Stock Options | Maximum
Stock Options and Stock Appreciation Rights
Continuous service period for awards to vest	3 years
Stock Appreciation Rights
Key assumptions used in Black-Scholes model to determine the fair value of each stock option and SAR
Weighted-average expected volatility (as a percent)	36.90%	36.60%	41.30%
Weighted-average expected life (in years)	5 years 4 months 24 days	5 years 3 months 18 days	4 years 9 months 18 days
Weighted-average dividend yield (as a percent)	1.00%	1.00%	1.00%
Weighted-average risk free interest rate (as a percent)	1.60%	1.70%	1.50%
Unrecognized stock-based compensation expense
Unrecognized compensation expense				$ 1,900
Weighted-average vesting period (years)	1 year 8 months 12 days
Contractual term of awards	10 years
Granted (in dollars per share)	$ 24.42	$ 21.15	$ 21.15	$ 18.35
Non-vested other than stock options, number of shares
Outstanding at the beginning of the period (in shares)	277,118
Granted (in shares)	97,817
Exercised (in shares)	(7,000)
Forfeited (in shares)	(130)
Outstanding at the end of the period (in shares)	367,805	277,118
Exercisable at the end of the period (in shares)				194,863
Other than stock options, weighted-average exercise price
Outstanding at the beginning of the period (in dollars per share)	$ 63.91
Granted (in dollars per share)	56.54
Exercised (in dollars per share)	30.96
Forfeited (in dollars per share)	62.14
Outstanding at the end of the period (in dollars per share)	$ 62.58	$ 63.91
Exercisable at the end of the period (in dollars per share)				$ 62.24
Other than stock options, weighted-average remaining contractual life (in years)
Outstanding at the end of the period	7 years 1 month 6 days
Exercisable at the end of the period	5 years 8 months 12 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value
Outstanding at the end of the period	$ 3,861
Exercisable at the end of the period				$ 2,106
Weighted-average grant date fair value (in dollars per share)	$ 24.42	$ 21.15	$ 21.15	$ 18.35
Total intrinsic value of SSARs exercised	$ 300	$ 200	$ 100
Other than stock options, weighted-average grant date fair value
Non-vested at the beginning of the period (in dollars per share)	$ 24.42	$ 21.15
Non-vested at the end of the period (in dollars per share)	$ 18.35	24.42	$ 21.15
Stock Appreciation Rights | Minimum
Stock Options and Stock Appreciation Rights
Continuous service period for awards to vest	1 year
Stock Appreciation Rights | Maximum
Stock Options and Stock Appreciation Rights
Continuous service period for awards to vest	3 years
Performance Shares
Unrecognized stock-based compensation expense
Unrecognized compensation expense				$ 2,300
Weighted-average vesting period (years)	1 year 6 months
Granted (in dollars per share)	$ 66.52	$ 66.52		$ 63.78
Non-vested other than stock options, number of shares
Outstanding at the beginning of the period (in shares)	200,325
Granted (in shares)	48,422
Vested (in shares)	(10,781)
Expired (in shares)	(23,750)
Forfeited (in shares)	(4,038)
Outstanding at the end of the period (in shares)	210,178	200,325
Other than stock options, weighted-average exercise price
Granted (in dollars per share)	$ 45.63
Expired (in dollars per share)	49.66
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value
Weighted-average grant date fair value (in dollars per share)	66.52	$ 66.52		$ 63.78
Other than stock options, weighted-average grant date fair value
Non-vested at the beginning of the period (in dollars per share)	66.52
Vested (in dollars per share)	75.06
Forfeited (in dollars per share)	35.15
Non-vested at the end of the period (in dollars per share)	$ 63.78	66.52
Performance Shares
Percentage of interim earn out basis for vesting, one				25.00%
Percentage of interim earn out basis for vesting, two				50.00%
Percentage of interim earn out basis for vesting, three				75.00%
Percentage of interim earn out basis for vesting, four				100.00%
Gold Equivalent Ounces Shares
Unrecognized stock-based compensation expense
Contractual term of awards	5 years
Gold Equivalent Ounces Shares | Vesting upon achievement of annual growth in Net GEOs
Unrecognized stock-based compensation expense
SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage	0.50%
Total Shareholder Return Shares
Stock Options and Stock Appreciation Rights
Continuous service period for awards to vest	3 years
Unrecognized stock-based compensation expense
Contractual term of awards	3 years
Granted (in dollars per share)	$ 35.15			$ 35.15
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value
Weighted-average grant date fair value (in dollars per share)	35.15			$ 35.15
Other than stock options, weighted-average grant date fair value
Non-vested at the end of the period (in dollars per share)	$ 35.15
Total Shareholder Return Shares | Vesting upon achievement of annual growth in Net TSR
Unrecognized stock-based compensation expense
SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage	0.50%
Restricted stock
Unrecognized stock-based compensation expense
Unrecognized compensation expense				$ 5,500
Weighted-average vesting period (years)	3 years
Granted (in dollars per share)	$ 66.23	$ 66.23		$ 63.46
Non-vested other than stock options, number of shares
Outstanding at the beginning of the period (in shares)	154,807
Granted (in shares)	73,187
Vested (in shares)	(51,472)
Outstanding at the end of the period (in shares)	176,522	154,807
Other than stock options, weighted-average exercise price
Granted (in dollars per share)	$ 56.25
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value
Weighted-average grant date fair value (in dollars per share)	66.23	$ 66.23		$ 63.46
Other than stock options, weighted-average grant date fair value
Non-vested at the beginning of the period (in dollars per share)	66.23
Vested (in dollars per share)	61.54
Non-vested at the end of the period (in dollars per share)	$ 63.46	$ 66.23
Restricted stock | Officers and Certain Employees
Non-vested other than stock options, number of shares
Granted (in shares)	50,507
Restricted Stock
Vesting period of awards granted to officers and certain employees	3 years
Holding period of awards granted to officers and certain employees, as a vesting condition	2 years
Fraction of the shares granted to officers and certain employees, vesting in year three	0.33%
Fraction of the shares granted to officers and certain employees, vesting in year four	0.33%
Fraction of the shares granted to officers and certain employees, vesting in year five	0.33%
Restricted stock | Non Executive Directors
Non-vested other than stock options, number of shares
Granted (in shares)	22,680
Restricted Stock
Vesting period of awards granted to officers and certain employees	1 year
Percentage of shares granted to non-executive directors, vesting immediately upon grant				50.00%
Percentage of shares granted to non-executive directors, vesting one year after date of grant				50.00%