Common Stock Repurchases - Additional Information (Detail) (Stock Repurchase Plan Two, USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended		1 Months Ended
	Jan. 31, 2014	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2014	Jan. 31, 2013	Dec. 08, 2011 Maximum
Stockholders Equity Note [Line Items]
Amount authorized for repurchase of Company's common stock						$ 30.0
Repurchase of common stock (in shares)	331,595	35,550	29,003	82,188	85,327
Repurchase of common stock	$ 23.4	$ 3.2	$ 2.1	$ 7.0	$ 6.0
Average purchase price of common stock	$ 70.47	$ 91.20	$ 71.91	$ 84.83	$ 70.56