INCOME TAXES (Details) (USD $)	3 Months Ended		12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2011
Income before income taxes
United States			$ 65,851,000	$ 110,189,000	$ 77,543,000
Foreign			71,317,000	42,830,000	38,730,000
Income before income taxes			137,168,000	153,019,000	116,273,000
Current:
Federal			30,061,000	35,556,000	28,783,000
State			368,000	310,000	105,000
Foreign			44,749,000	17,273,000	15,222,000
Total current income tax expenses			75,178,000	53,139,000	44,110,000
Deferred and others:
Federal			(4,341,000)	77,000	(1,242,000)
State			(27,000)
Foreign			(7,051,000)	1,494,000	(3,894,000)
Total deferred and other income tax expenses			(11,419,000)	1,571,000	(5,136,000)
Total income tax expenses			63,759,000	54,710,000	38,974,000
Differences between provision for income taxes and income tax expense computed by applying federal rates
Total expense computed by applying federal rates			48,009,000	53,557,000	40,695,000
State and provincial income taxes, net of federal benefit			368,000	310,000	105,000
Adjustments of valuation allowance				(1,007,000)	(346,000)
Excess depletion			(1,395,000)	(1,416,000)	(1,446,000)
Estimates for uncertain tax positions			1,868,000	551,000	437,000
Statutory tax attributable to non-controlling interest			(1,236,000)	(2,042,000)	(2,066,000)
Effect of foreign earnings			4,223,000	511,000	(891,000)
Effect of recognized loss on available-for-sale securities			4,239,000
Unrealized foreign exchange gains			1,146,000	(546,000)	2,548,000
True up of prior year tax returns			4,979,000
True-up of prior year deferred assets				1,075,000
Excess 162(m) compensation			1,272,000	1,116,000	215,000
Other			286,000	2,601,000	(277,000)
Total income tax expenses			63,759,000	54,710,000	38,974,000
Deferred tax assets:
Stock-based compensation	3,853,000		3,853,000	3,984,000
Net operating losses	25,943,000		25,943,000	23,815,000
Other deferred tax assets	4,460,000		4,460,000	2,615,000
Total deferred tax assets	34,256,000		34,256,000	30,414,000
Valuation allowance	(4,606,000)		(4,606,000)	(500,000)
Net deferred tax assets	29,650,000		29,650,000	29,914,000
Deferred tax liabilities:
Mineral property basis	(165,936,000)		(165,936,000)	(172,146,000)
Unrealized foreign exchange gains	(3,684,000)		(3,684,000)	(4,414,000)
2019 Notes	(23,281,000)		(23,281,000)	(27,126,000)
Other deferred tax liabilities	(3,561,000)		(3,561,000)	(4,117,000)
Total deferred tax liabilities	(196,462,000)		(196,462,000)	(207,803,000)
Total net deferred taxes	(166,812,000)		(166,812,000)	(177,889,000)
Valuation allowances
Increase in valuation allowances as a result of the recognized and unrealized loss on available-for-sale securities			4,100,000
Net operating loss carry forwards
Net operating loss carry forwards	108,000,000		108,000,000	95,000,000
Increase in the net operating loss carry forwards offset by the utilization of net operating losses in non-U.S. subsidiaries			26,000,000
Reconciliation of beginning and ending amount of gross unrecognized tax benefits
Total gross unrecognized tax benefits at beginning of year			19,469,000	18,836,000	12,479,000
Additions / Reductions for tax positions of prior years					20,000
Additions / Reductions for tax positions of current year			2,638,000	2,051,000	6,337,000
Reductions due to settlements with taxing authorities			(941,000)
Reductions due to lapse of statute of limitations				(1,418,000)
Total amount of gross unrecognized tax benefits at end of year	21,166,000		21,166,000	19,469,000	18,836,000
Net unrecognized tax benefits
Unrecognized tax benefits included in tax expense, recorded on additional pre-tax income from non-U.S. subsidiaries	1,100,000		1,100,000
Expiration period of statute of limitations for income tax examinations			12 months
Decrease in net unrecognized income tax benefits, reasonably possible in the next 12 months, lower bound	0		0
Decrease in net unrecognized income tax benefits, reasonably possible in the next 12 months, upper bound	300,000		300,000
Accrued income-tax-related interest and penalties	4,300,000		4,300,000	2,800,000
Foreign withholding tax payment	12,000,000	17,200,000
Foreign withholding tax recovered	2,300,000	8,500,000
Income tax receivable
Income taxes
Income tax receivable related to foreign withholding tax	8,700,000		8,700,000
Prepaid expenses and other current assets
Income taxes
Income tax receivable related to foreign withholding tax	$ 9,700,000		$ 9,700,000