Earnings Per Share and Dividends - Additional Information (Detail) (USD $)	0 Months Ended			3 Months Ended			9 Months Ended		0 Months Ended
	Sep. 03, 2014	Jun. 05, 2014	Apr. 18, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2014	Sep. 30, 2013	Nov. 06, 2014 Subsequent Event
Dividends Payable [Line Items]
Distributions declared per Class A common stock				$ 0.0625	$ 0.0625	$ 0.0625
Distributions declared per Class A common stock, payable date									Dec. 04, 2014
Distributions declared per Class A common stock, record date									Nov. 20, 2014
Dividends to Class A common stockholders	$ 724,000	$ 724,000	$ 725,000				$ 2,173,000	$ 0
Dividends declared							$ 2,173,000	$ 0