XML 17 R55.htm IDEA: XBRL DOCUMENT v2.4.0.6
ASSET RETIREMENT OBLIGATIONS, CONTRACTUAL THIRD-PARTY RECLAMATION RECEIVABLES, AND RECLAMATION DEPOSITS - Changes in Company's Asset Retirement Obligations (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Dec. 31, 2012
Asset Retirement Obligation Disclosure [Abstract]      
Asset retirement obligations, beginning of period (including current portion) $ 263,847 $ 247,478  
Accretion 5,481 5,283  
Liabilities settled (5,839) (4,411)  
Changes due to amount and timing of reclamation 0 (4,757)  
ARO acquired 0 15,103  
Asset retirement obligations, end of period 263,489 258,696  
Less current portion (23,154) (16,050) (22,238)
Asset retirement obligations, less current portion $ 240,335 $ 242,646 $ 241,609