Employee Benefits - Summary of SERPs and Defined Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Benefits
Balances in Deferred Compensation Plan	$ 31.4	$ 21.8
Value of assets for funding future payouts under the deferred compensation plan	26.5	21.1
Contributions to Multiemployer Plans	5.7	5.4	$ 5.4
Change in plan assets
Fair value of plan assets at beginning of year	94.9
Fair value of plan assets at end of year	107.1	94.9
Amounts recognized in the statement of financial position
Noncurrent liabilities	(87.0)	(71.8)
SERPs
Change in benefit obligation
Benefit obligation at beginning of year	37.2	36.6
Service cost	0.9	0.9	0.8
Interest cost	1.4	1.1	1.1
Actuarial loss (gain)	11.4	(0.3)
Benefits paid	(1.1)	(1.1)
Benefit obligation at end of year	49.8	37.2	36.6
Funded status
Funded status of the plans	(49.8)	(37.2)
Items not yet recognized as component of net periodic pension expense
Unrecognized net actuarial losses	19.6	9.1
Accumulated other comprehensive loss	19.6	9.1
Amounts recognized in the statement of financial position
Current liabilities	(17.5)	(1.1)
Noncurrent liabilities	(32.3)	(36.1)
Accumulated other comprehensive loss	19.6	9.1
Net amount recognized	(30.2)	(28.1)
Accumulated benefit obligation	42.0	32.5
Components of net periodic benefit cost
Service cost	0.9	0.9	0.8
Interest cost	1.4	1.1	1.1
Settlement loss			3.7
Amortization of net loss	1.0	0.9	0.9
Net periodic benefit cost	$ 3.3	$ 2.9	$ 6.5
Weighted average assumptions to determine net cost
Discount rate (as a percent)	3.81%	3.04%	3.36%
Rate of compensation increase (as a percent)	6.00%	6.00%	6.00%
Weighted average assumptions to determine benefit obligations
Discount rate (as a percent)	2.63%	3.82%
Rate of compensation increase (as a percent)	6.00%	6.00%
Expected employer contributions during 2020	$ 17.5
Defined Benefit Plans
Change in benefit obligation
Benefit obligation at beginning of year	96.6	$ 103.5
Service cost	1.6	1.7	$ 1.5
Interest cost	3.8	3.5	3.7
Actuarial loss (gain)	15.9	(9.3)
Benefits paid	(3.9)	(3.8)
Plan amendments	2.2	1.0
Benefit obligation at end of year	116.2	96.6	103.5
Change in plan assets
Fair value of plan assets at beginning of year	94.9	89.0
Actual return on plan assets	16.1	(4.2)
Employer contributions		13.9
Benefits paid	(3.9)	(3.8)
Fair value of plan assets at end of year	107.1	94.9	89.0
Funded status
Funded status of the plans	(9.1)	(1.7)
Items not yet recognized as component of net periodic pension expense
Unrecognized net actuarial losses	27.2	23.2
Unamortized prior service cost	4.7	2.8
Accumulated other comprehensive loss	31.9	26.0
Amounts recognized in the statement of financial position
Noncurrent liabilities	(9.1)	(1.7)
Accumulated other comprehensive loss	31.9	26.0
Net amount recognized	22.8	24.3
Accumulated benefit obligation	116.2	96.6
Information for defined benefit plans with an accumulated benefit obligation and projected benefit obligation in excess of plan assets
Accumulated benefit obligation	116.2	53.0
Projected benefit obligation	116.2	53.0
Fair value of plan assets	107.1	50.1
Components of net periodic benefit cost
Service cost	1.6	1.7	1.5
Interest cost	3.8	3.5	3.7
Expected return on plan assets	(5.6)	(5.1)	(4.4)
Settlement loss			0.1
Prior service (credit) cost	0.4	0.3	0.3
Amortization of net loss	1.3	1.4	1.5
Net periodic benefit cost	$ 1.5	$ 1.8	$ 2.7
Weighted average assumptions to determine net cost
Discount rate (as a percent)	4.06%	3.47%	3.93%
Expected long-term rate of return on plan assets (as a percent)	6.09%	5.66%	6.17%
Weighted average assumptions to determine benefit obligations
Discount rate (as a percent)	2.59%	4.06%
Expected long-term rate of return on plan assets (as a percent)	6.09%	5.66%
Expected employer contributions during 2020	$ 1.8
Warehouse, delivery, selling, general and administrative expense | SERPs
Components of net periodic benefit cost
Net periodic benefit cost	0.9	$ 0.9	$ 0.8
Warehouse, delivery, selling, general and administrative expense | Defined Benefit Plans
Components of net periodic benefit cost
Net periodic benefit cost	1.6	1.7	1.5
Other (income) expense, net | SERPs
Components of net periodic benefit cost
Net periodic benefit cost	2.4	2.0	5.7
Other (income) expense, net | Defined Benefit Plans
Components of net periodic benefit cost
Net periodic benefit cost	$ (0.1)	$ 0.1	$ 1.2