Earnings Per Share - Summary of Number of Participating Securities and Earning Allocated to those Securities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Earnings allocated to participating shareholders	$ 0us-gaap_UndistributedEarningsDiluted	$ 0us-gaap_UndistributedEarningsDiluted
Number of participating securities	1.1hbp_NumberOfParticipatingSecurities	1.4hbp_NumberOfParticipatingSecurities

The earnings that is allocated to common stock and participating securities to the extent that each security may share in earnings as if all of the earnings for the period had been distributed. Includes the adjustments resulting from the assumption that dilutive securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

No definition available.

Name:	us-gaap_UndistributedEarningsDiluted
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration