Accounts Payable and Accrued Liabilities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Accounts payable due to bank	$ 14.7bdc_AccountsPayableDueToBankCurrent	$ 16.1bdc_AccountsPayableDueToBankCurrent
Settlement of accounts payable outstanding	1 year

Term of settlement of accounts payable due to bank.

No definition available.

Name:	bdc_TermOfSettlementOfAccountsPayableDueToBank
Namespace Prefix:	bdc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration