Stockholder's Equity - Additional Information (Detail) - Jul. 22, 2015 - Subsequent Event - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Total
Stockholders' Equity [Line Items]
Shares issued in equity offering	18.4
Price per share received in equity offering	$ 54.50
Proceeds from issuance of common stock, net	$ 969