Stockholders' Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	6 Months Ended
	Sep. 17, 2014	Jan. 31, 2015	Sep. 15, 2011
Class of Stock [Line Items]
Underwritten public offering, number of common stock closed	4,682,927
Underwritten public offering, price per share	$ 10.25
Underwriters' option to purchase additional shares to cover over-allotments, duration	30 days
Underwritten public offering net of underwriting discounts and commissions and offering expenses	$ 52.1
Repayment of portion of outstanding principal	20
Common Stock
Class of Stock [Line Items]
Stock repurchase program, authorized amount			25
Share repurchase program, term		The Company will determine the timing and amount of the transactions based on its evaluation of market conditions and other factors. The repurchase program may be suspended or discontinued at any time and has no expiration date.
Stock repurchased during period, shares		3,294,666
Stock repurchased during period, value		$ 18.7
Additional restructuring charges
Class of Stock [Line Items]
Underwritten public offering, number of common stock closed	702,439