Dividends Paid - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended
	Mar. 18, 2014	Jan. 21, 2014	Mar. 31, 2014	Mar. 31, 2013
Dividends Payable [Line Items]
Dividends declared per common share	$ 0.30	$ 0.30	$ 0.60	$ 0.54
Cash dividend, payment date	May 15, 2014	Feb. 18, 2014
Cash dividend, record date	May 01, 2014	Feb. 03, 2014
Cash dividend, declaration date	Mar. 18, 2014	Jan. 21, 2014