XML 31 R57.htm IDEA: XBRL DOCUMENT v2.4.0.6
Financial instruments - Fair Value Amounts of Derivative Instruments and Their Effect on Statement of Operations (Parenthetical) (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]  
Ineffective portion of derivative included in income $ 0