Equity - Additional Information (Detail) $ in Millions	6 Months Ended
Jun. 30, 2017 USD ($) Class shares
Class Of Stock Disclosures [Abstract]
Number of classes of common stock \| Class	4
Number of Shares, Authorized to issue, Total	2,100,000,000
Common stock, shares issued	88,930,421
Net proceeds from issuance of common stock \| $	$ 890.3

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_CommonStockSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant