Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2017
Schedule Of Pre Tax Income [Line Items]
Excess tax benefits on share based payments	$ 3.8	$ 14.8
Earliest Tax Year [Member] \| New York State [Member]
Schedule Of Pre Tax Income [Line Items]
Income tax year under examination		2010
Latest Tax Year [Member] \| New York State [Member]
Schedule Of Pre Tax Income [Line Items]
Income tax year under examination		2013

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration