Dividends - Additional Information (Detail) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 17, 2015	Jan. 20, 2015
Dividends Payable [Line Items]
Dividends declared per common share	$ 0.43	$ 0.60
Dividend Declared
Dividends Payable [Line Items]
Dividends declared per common share			$ 0.10	$ 0.33
Cash dividend, date dividend paid			May 15, 2015	Feb. 17, 2015
Cash dividend, record date			May 01, 2015	Feb. 02, 2015
Cash dividend, declaration date			Mar. 17, 2015	Jan. 20, 2015