Summary of Quarterly Results - Summary of Unaudited Quarterly Financial Information (Parenthetical) (Detail) (USD $)	12 Months Ended			3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2013 Discontinued Operations [Member]	Mar. 31, 2013 Discontinued Operations [Member]	Dec. 31, 2012 Discontinued Operations [Member]
Quarterly Results Of Operations [Line Items]
Impairment losses				$ 23,700,000		$ 3,800,000
Gains on sales of discontinued operations	$ 78,512,000	$ 947,000	$ 0	$ 45,100,000	$ 33,400,000	$ 900,000