Dividends Paid - Additional Information (Detail) (USD $)	1 Months Ended	6 Months Ended		1 Months Ended
	Mar. 18, 2014	Jun. 30, 2014	Jun. 30, 2013	Jul. 22, 2014 Subsequent Event
Dividends Payable [Line Items]
Dividends declared per common share	$ 0.30	$ 0.60	$ 0.54	$ 0.33
Cash dividend, payment date	May 15, 2014			Aug. 15, 2014
Cash dividend, record date	May 01, 2014			Aug. 01, 2014
Cash dividend, declaration date	Mar. 18, 2014			Jul. 22, 2014