Summary of Quarterly Results - Summary of Unaudited Quarterly Financial Information(Detail) (USD $)	3 Months Ended			12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Results Of Operations [Line Items]
Impairment losses	$ 2,300,000	$ 16,100,000	$ 1,300,000
Gains on sales of discontinued operations				78,512,000	947,000
Discontinued Operations [Member]
Quarterly Results Of Operations [Line Items]
Impairment losses	23,700,000
Gains on sales of discontinued operations	$ 45,100,000		$ 33,400,000