Debt, Capital Leases and Royalty Obligation (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Long term debt and capital lease obligations
Current	$ 55,983	$ 32,602
Non-current	3,460	115,861
Interest expenses incurred for various debt instruments
Accretion of Franco Nevada royalty obligation	19,139	22,230	20,502
Amortization of debt issuance costs	1,146	2,050	4,047
Accretion of debt discount	2,536	2,324	2,543
Capitalized interest	(2,663)	(2,175)	(9,885)
Total interest expense, net of capitalized interest	26,169	34,774	30,942
3.25% Convertible Senior Notes due March 2028 [Member]
Long term debt and capital lease obligations
Current	48,081	0
Non-current	0	45,545
Interest expenses incurred for various debt instruments
Interest Expense	1,581	1,581	2,394
1.25% Convertible Senior Notes due January 2024 (terminated in 2011) [Member]
Interest expenses incurred for various debt instruments
Interest Expense	0	1	28
Senior Term Notes due December 31, 2012 [Member]
Interest expenses incurred for various debt instruments
Interest Expense	0	1,381	5,074
Kensington Term Facility [Member]
Long term debt and capital lease obligations
Current	0	15,398
Non-current	0	60,425
Interest expenses incurred for various debt instruments
Interest Expense	2,339	4,383	2,017
Gold lease facility [Member]
Interest expenses incurred for various debt instruments
Interest Expense	0	0	677
Capital Lease Obligations [Member]
Long term debt and capital lease obligations
Current	7,902	17,119
Non-current	3,460	9,891
Interest expenses incurred for various debt instruments
Interest Expense	997	1,620	2,122
Other debt obligations [Member]
Interest expenses incurred for various debt instruments
Interest Expense	1,094	1,379	1,423
Other [Member]
Long term debt and capital lease obligations
Current	0	85
Non-current	$ 0	$ 0