Common Stock Repurchase Plan (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2014
Common Stock Repurchase Plan [Abstract]
Common shares repurchased to treasury during period (in shares)	375
Aggregate cost of shares repurchased during period	$ 446
Total number of common shares authorized for repurchase (in shares)	10,000
Total number of common shares repurchased to date (in shares)	6,163
Total number of shares that may yet be repurchased (in shares)	3,837

Equity impact of the aggregate cost of common stock repurchased during the period that are being held in treasury.

No definition available.

Name:	abcp_AggregateCostOfSharesRepurchasedDuringPeriod
Namespace Prefix:	abcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Number of shares of common stock repurchased during the period that are being held in treasury.

No definition available.

Name:	abcp_CommonStockSharesRepurchasedForTreasury
Namespace Prefix:	abcp_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Number of shares that have been repurchased during pursuant to the Repurchase Plan.

No definition available.

Name:	abcp_SharesAcquiredPursuantToRepurchasePlan
Namespace Prefix:	abcp_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

No definition available.

Name:	us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

No definition available.

Name:	us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant