Impairment Charges and Impairment of Joint Venture Investments - Impairment Charges on Assets or Investments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Impairment Charges And Impairment Of Joint Venture Investments [Abstract]
Assets marketed for sale or asset sold	$ 0	$ 0	$ 179,700	$ 3,000
Total continuing operations	0	1,448	279,021	18,119
Sold assets – discontinued operations	0	365	0	8,877
Joint venture investments	0	0	0	9,100
Total impairment charges	0	1,800	279,000	36,100
Undeveloped Land [Member]
Impairment Charges And Impairment Of Joint Venture Investments [Abstract]
Undeveloped land previously held for development	$ 0	$ 1,400	$ 99,300	$ 15,100