Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Topic 470
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-Section 50
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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 210
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Debt - Schedule of Debt Obligations (Parenthetical) (Detail) $ in Millions, $ in Millions, $ in Millions	Sep. 30, 2021 USD ($)	Sep. 30, 2021 AUD ($)	Mar. 31, 2021	Dec. 31, 2020 USD ($)	Dec. 31, 2020 CAD ($)	Apr. 30, 2018 USD ($)
Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate on debt	0.25%	0.25%	0.25%	0.25%	0.25%
Term Debt [Member]
Debt Instrument [Line Items]
Interest rate on debt	2.60%	2.60%		2.60%	2.60%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Available capacity	$ 300.0			$ 300.0		$ 300.0
Revolving Credit Facility [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Available capacity	2.3			0.4
Foreign Line of Credit [Member] \| Australia [Member]
Debt Instrument [Line Items]
Available capacity	$ 2.0
Foreign Line of Credit [Member] \| Australia [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Available capacity		$ 2.8
Foreign Line of Credit [Member] \| Canada [Member]
Debt Instrument [Line Items]
Available capacity				$ 5.4
Foreign Line of Credit [Member] \| Canada [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Available capacity					$ 7.0