Subsequent Events - Additional Information (Detail) - $ / shares	Jul. 29, 2015	May. 07, 2015	Feb. 19, 2015
Subsequent Event [Line Items]
Cash dividend declaration per share		$ 1.69	$ 1.69
Special distribution, payable date		Jun. 17, 2015	Mar. 25, 2015
Dividends payable, date of Record		May 27, 2015	Mar. 11, 2015
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends declared date	Jul. 29, 2015
Cash dividend declaration per share	$ 1.69
Special distribution, payable date	Sep. 16, 2015
Dividends payable, date of Record	Aug. 26, 2015