Employee Benefit and Retirement Plans - Composition of Domestic Pension Plan Assets (Detail) - U.S. - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	$ 1,228.2	$ 1,104.9
Fair Value Measurements, Subtotal
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	473.2	478.7
NAV-based assets
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	755.0	626.2
Global equities
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	232.5	179.8
Global equities | Fair Value Measurements, Subtotal
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	0.0	0.0
Global equities | NAV-based assets
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	232.5	179.8
Fixed income securities and funds
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	730.0	682.6
Fixed income securities and funds | Fair Value Measurements, Subtotal
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	400.0	413.3
Fixed income securities and funds | NAV-based assets
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	330.0	269.3
Alternative investments
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	239.4	217.8
Alternative investments | Fair Value Measurements, Subtotal
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	46.9	40.7
Alternative investments | NAV-based assets
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	192.5	177.1
Other contract
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	26.3	24.7
Other contract | Fair Value Measurements, Subtotal
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	26.3	24.7
Other contract | NAV-based assets
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	0.0	0.0
Level 1
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	456.9	462.9
Level 1 | Global equities
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets		0.0
Level 1 | Fixed income securities and funds
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	400.0	413.3
Level 1 | Alternative investments
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	46.9	40.7
Level 1 | Other contract
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	10.0	8.9
Level 2
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	15.2	14.8
Level 2 | Global equities
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets		0.0
Level 2 | Fixed income securities and funds
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets		0.0
Level 2 | Alternative investments
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets		0.0
Level 2 | Other contract
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	15.2	14.8
Level 3
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	1.1	1.0
Level 3 | Global equities
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets		0.0
Level 3 | Fixed income securities and funds
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets		0.0
Level 3 | Alternative investments
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets		0.0
Level 3 | Other contract
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined benefit plan, fair value of plan assets	$ 1.1	$ 1.0