Common Stock - Additional Information (Detail) (Underwriter [Member], USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended
	Jul. 31, 2014
Underwriter [Member]
Class Of Stock [Line Items]
Number of shares issued through underwriting agreement	15,500,000
Shares offered, price per share	$ 18.10
Additional shares to be offered under underwriting agreement	2,300,000
Number of days option granted to underwriters	30 days
Proceeds from issuance to underwriters	$ 21
Underwriters exercised this option for an additional, shares	1,200,000
Net proceeds from offering through the underwriting	$ 271