Stockholders' Equity - Additional Information (Detail) shares in Millions	Sep. 30, 2018 shares
Equity [Abstract]
Maximum number of shares authorized to be repurchased	9.1

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

No definition available.

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