Effect of New Accounting Pronouncements - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Right-of-use assets	$ 373.9	$ 393.5	$ 379.6
Operating lease liabilities	409.7		420.3
Net rent related asset and liabilities			38.3
Retained earnings	$ 2,371.7	$ 1,901.3
ASU 2016-02 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2019
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	false
ASU 2016-13 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
ASU 2018-13 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
ASU 2018-14 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
ASU 2017-12 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2019
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	false
ASU 2017-04 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
ASU 2018-15 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
Cumulative Effect Period Of Adoption Adjustment [Member] | ASU 2016-02 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings			(2.4)
Cumulative Effect Period Of Adoption Adjustment [Member] | ASU 2017-12 [Member] | Accumulated Other Comprehensive Loss [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings			$ 0.2