The increases or decreases in lease payments that result from changes occurring after the inception of the lease in the factors (other than the passage of time) on which lease payments are based, except that any escalation of minimum lease payments relating to increases in construction or acquisition cost of the leased property or for increases in some measure of cost or value during the construction or preconstruction period, are excluded from contingent rentals. Contingent rentals also may include amounts for which the triggering events have not yet occurred or the specified targets for which have not yet been achieved (such as sales based percentage rent), but which events are considered probable of occurring or which specified targets are considered probable of being achieved.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Contingent Rentals
-URI http://asc.fasb.org/extlink&oid=6508509

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 40
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6452616&loc=d3e36728-112689

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 25
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=7579899&loc=d3e35050-112683

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6452660&loc=d3e36991-112694

Name:	us-gaap_OperatingLeasesRentExpenseContingentRentals
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Subsequent Event - Additional Information (Detail) $ in Millions	Jan. 01, 2018 ft²	Aug. 15, 2017 ft²	May 09, 2017 USD ($) ft²
Sixth Amendment to Lease [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Increased office space rent			32,876
Lease expiration date			Aug. 15, 2024
Increase in future expected payments \| $			$ 15.8
Sixth Amendment to Lease [Member] \| Scenario Forecast [Member]
Subsequent Event [Line Items]
Increased office space rent	24,676	8,200
Sixth Amendment to Lease [Member] \| Scenario Forecast [Member] \| Maximum [Member]
Subsequent Event [Line Items]
Additional space expiration term		84 months
Before Sixth Amendment to Lease [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Lease expiration date			Mar. 01, 2022