Share capital (Narrative) (Details) (USD $)	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended	110 Months Ended		6 Months Ended	1 Months Ended	6 Months Ended				6 Months Ended				6 Months Ended	1 Months Ended		6 Months Ended
	Apr. 30, 2012	Mar. 31, 2012	May 31, 2013	May 31, 2012	May 31, 2013	May 31, 2012	Nov. 30, 2012	May 31, 2013	May 31, 2013 Performance Share Units [Member]	May 31, 2013 Number of RSU's [Member]	Apr. 30, 2012 Plan of Arrangement [Member]	May 31, 2013 Number of DSU's [Member]	May 31, 2013 Stock-based Compensation [Member]	May 31, 2013 NovaGold Arrangement Options [Member]	Nov. 30, 2012 NovaGold Arrangement Options [Member]	May 31, 2013 Approximations [Member]	May 31, 2013 Approximations [Member] Stock-based Compensation [Member]	May 31, 2013 Minimum [Member]	May 31, 2013 Maximum [Member]	May 31, 2013 Director [Member] Approximations [Member]	Jun. 30, 2013 Employees [Member]	Jun. 30, 2013 Employees [Member] Number of RSU's [Member]	May 31, 2013 Employees [Member] Approximations [Member]
Stock issued under the Plan of Arrangement	200	46,578,078					46,577,878				46,578,078
Stock issued pursuant to employment agreement							76,005
Common stock committed for issuance											6,181,352
Contributed surplus			$ 151,000		$ 151,000		$ 12,180,000	$ 151,000			$ 12,200,000
Common Stock, Shares Authorized									100,000
Percentage of PSU's to be issued from amount granted																		0.00%	150.00%
Stock options granted					35,000									2,189,040
Stock options exercised					1,184		10,986							(3,822)
Stock options granted, weighted average exercise price					$ 0.72									$ 1.26
Share-based payments			2,000,000	5,494,000	6,113,000	5,494,000		16,637,000								1,000,000	1,700,000			1,400,000			300,000
Non-vested stock options outstanding			5,939,996		5,939,996		6,064,994	5,939,996				20,685		1,944,179	2,076,541
Weighted average exercise price options outstanding			$ 2.97		$ 2.97		$ 2.98	$ 2.97						$ 4.11	$ 4.05
Stock option expense			0	316,000	0	316,000		316,000
Common Shares Distributed			52,769,927	46,603,329	48,588,311	46,626,140
Stockholders' Equity, Spinoff Transaction	64,500,000
Stock Issued on Vesting of Performance Share Units					16,586
Stock Issued on Exercise of Warrants					6,088,262
Value of Stock Issued on Exercise of Warrants					11,996,000											12,000,000
Stock-based Compensation for NovaGold Arrangement Options													50,000
Granted										295,500		750,000
Stock Issued During Period, Value, Share-based Compensation																	$ 3,300,000
Units vested																						94,496
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures																					94,496