XML 18 R46.htm IDEA: XBRL DOCUMENT v2.4.0.8
Variable Interest Entities - Royalty Trusts - Outstanding Units (Parenthetical) (Details) (Royalty Trusts)
6 Months Ended
Jun. 30, 2014
Royalty Trusts
 
Variable Interest Entity  
Percentage of royalty interest conveyed to company at trust termination 50.00%
Percentage of royalty interest sold at trust termination 50.00%