Acquisitions and Dispositions - Additional Information (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2015 USD ($) Partnership Trust	Sep. 30, 2014 USD ($)
Business Combinations [Abstract]
Number of limited partnerships \| Partnership	18
Number of business income trusts	2
Purchase of non-controlling interests \| $	$ 101	$ 233

The cash outflow during the period for redemption of redeemable noncontrolling interests.

No definition available.

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