Impairment Provisions (Summary of Impairment Provisions) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Impaired Long-Lived Assets Held and Used [Line Items]
Provision for impairment	$ 9,669		$ 1,387		$ 16,917
Provision for impairment related to investments in real estate	0		386		9,611
Total	9,669		4,688		37,411
Land held for development or available for sale
Impaired Long-Lived Assets Held and Used [Line Items]
Provision for impairment	327	[1]	1,387	[1]	11,468	[1]
Income producing properties marketed for sale
Impaired Long-Lived Assets Held and Used [Line Items]
Provision for impairment	$ 9,342	[2]	$ 2,915	[2]	$ 16,332	[2]

[1] In 2013, changes to estimated sales price assumptions triggered an impairment provision of $0.3 million. Refer to Note 1 under Accounting for the Impairment of Long-Lived Assets for a discussion of inputs used in determining the fair value of long-lived assets.

[2] In 2013, our decision to market for potential sale certain wholly-owned income producing properties resulted in an impairment provision of $9.4 million. Refer to Note 1 under Accounting for the Impairment of Long-Lived Assets for a discussion of inputs used in determining the fair value of long-lived assets.