Credit Agreement - Schedule of Credit Agreement (Parenthetical) (Detail) - Credit Agreement [Member] - BMO Harris Bank N.A. ("BMO Harris") [Member]	Dec. 31, 2020 USD ($)
Letter of Credit [Member]
Line Of Credit Facility [Line Items]
Letters of credit, borrowing limit under the credit agreement	$ 50,000,000.0
Letter of Credit Sublimit [Member]
Line Of Credit Facility [Line Items]
Letters of credit, borrowing limit under the credit agreement	$ 25,000,000.0

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant