v2.4.1.9
Realized and Net Change in Unrealized Gains (Losses) on Investments (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Gain (Loss) on Investments [Line Items]    
Realized Gains $ 22bx_RealizedGainsLossesOnOtherInvestments $ 6,307bx_RealizedGainsLossesOnOtherInvestments
Net Change in Unrealized Gains (Losses) 371bx_NetChangeInUnrealizedGainsLossesOnOtherInvestments (6,504)bx_NetChangeInUnrealizedGainsLossesOnOtherInvestments
Total realized and net change in unrealized gains (losses) $ 393us-gaap_GainLossOnSaleOfOtherInvestments $ (197)us-gaap_GainLossOnSaleOfOtherInvestments