Supplemental Financial Statement Information - Summary of Information Related to Sale of Shares (Detail) (Hydrogenics [Member], USD $)
In Thousands, except Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Hydrogenics [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Shares sold 172,000 0
Proceeds received $ 2,493 $ 0
Pretax gain realized $ 2,363 $ 0