Fair Value Measurements Quantitative information related to Level III inputs (Details) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Corporate securities	$ 15,205	$ 15,410
Level III [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Corporate securities	490	488
Level III [Member] \| Third Party Trading Desk [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Corporate securities	$ 490	$ 488

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents corporate securities as of the balance sheet date.

No definition available.

Name:	mbrg_CorporateSecuritiesFairValueDisclosure
Namespace Prefix:	mbrg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant