ACQUISITIONS (Details)	9 Months Ended		0 Months Ended							9 Months Ended			0 Months Ended
	Mar. 31, 2013 USD ($)	Mar. 31, 2012 USD ($)	Dec. 13, 2012 Seabridge Gold, Inc. Additional Shares USD ($) item	Dec. 13, 2012 Seabridge Gold, Inc. Additional Shares CAD	Dec. 13, 2012 Seabridge Gold, Inc. NSR Royalty Option 1 CAD	Dec. 13, 2012 Seabridge Gold, Inc. NSR Royalty Option 2 CAD	Mar. 01, 2013 Mt. Milligan USD ($)	Dec. 03, 2012 Mt. Milligan USD ($)	Sep. 03, 2012 Mt. Milligan USD ($)	Mar. 31, 2013 Mt. Milligan USD ($)	Aug. 08, 2012 Mt. Milligan USD ($)	Jul. 31, 2012 Mt. Milligan USD ($)	Aug. 15, 2012 Milligan III Acquisition USD ($)	Aug. 08, 2012 Milligan III Acquisition USD ($)
Acquisition of Royalty Interest in Mineral Properties
Percentage of payable ounces of gold purchased											52.25%			12.25%
Total purchase amount											$ 781,500,000	$ 581,500,000		$ 200,000,000
Cash payment for each payable ounce of gold (in dollars per ounce)											435
Inflation adjustment											0
Cash paid for acquisition of royalty interests	277,081,000	193,662,000					62,000,000	95,000,000	45,000,000				75,000,000
Total cash paid on pre-production commitment										731,600,000
Future scheduled payments due for second quarter in calendar year 2013										37,000,000
Future scheduled payments due for third quarter in calendar year 2013										12,900,000
Common shares acquired in a private placement			1,004,491	1,004,491
Premium on share price as a percentage of the volume weighted-average trading price of common shares			15.00%	15.00%
Trading period used to calculate premium on share price			5 days	5 days
Payment made for common shares acquired			18,300,000	18,000,000
Holding period of shares as a condition to acquire additional shares			270 days	270 days
Proceeds from sale of shares in private transaction			14,600,000	14,400,000
Additional percentage of royalty that can be acquired			0.75%	0.75%
Percentage of royalty that can be acquired					1.25%	2.00%
Purchase price of royalty					100,000,000	160,000,000
Number of installments in which the purchase price of royalty is payable			3	3
Installment period in which the purchase price of royalty is payable			540 days	540 days
Premium on share price			2,400,000
Realized loss on trading securities			$ 1,300,000