Concentration of Credit Risks of Financial Instruments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Financial Instruments [Line Items]
Cash in bank deposit accounts in excess of the FDIC insured amount	$ 250,000

Cash Balance On Bank Deposit In Excess Of Fdic Insured Amount

No definition available.

Name:	bzc_CashBalanceOnBankDepositInExcessOfFdicInsuredAmount
Namespace Prefix:	bzc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant