Impairment Charges and Impairment of Joint Venture Investments - Impairment Charges on Assets or Investments (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Impairment Charges And Impairment Of Joint Venture Investments [Abstract]
Land held for development	$ 13,200,000	$ 0	$ 13,200,000	$ 0
Undeveloped land	0	2,600,000	400,000	2,600,000
Assets marketed for sale	1,100,000	11,000,000	11,000,000	11,000,000
Total continuing operations	14,342,000	13,642,000	24,615,000	13,642,000
Sold assets – discontinued operations	0	21,338,000	568,000	29,017,000
Joint venture investments	0	0	9,100,000	0
Total impairment charges	$ 14,300,000	$ 34,900,000	$ 34,300,000	$ 42,600,000