Acquisitions and Dispositions - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2014 Trust Investment	Jun. 30, 2013
Business Combinations [Abstract]
Number of limited partnerships	18
Number of business income trusts	2
Purchase of non-controlling interests	$ 209	$ 7

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