Employee Benefit Plans - Defined Benefit Pension Plans (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) $ / item	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Short-term investments
Employee benefit plans
Value of short-term investments (in dollars per unit) \| $ / item	1.00
Pension plans
Employee benefit plans
Fair value of plan assets		$ 425.2
Pension plans \| Global equity common trust funds
Employee benefit plans
Fair value of plan assets		57.6
Pension plans \| Fixed income common trust funds
Employee benefit plans
Fair value of plan assets		163.1
Pension plans \| Commingled global fund allocation
Employee benefit plans
Fair value of plan assets		80.6
Pension plans \| Corporate bonds
Employee benefit plans
Fair value of plan assets		29.1
Pension plans \| Non-U.S. Government securities
Employee benefit plans
Fair value of plan assets		39.0
Pension plans \| U.S. Government securities
Employee benefit plans
Fair value of plan assets		31.1
Pension plans \| Short-term investments
Employee benefit plans
Fair value of plan assets		10.5
Pension plans \| Global Equity Securities
Employee benefit plans
Fair value of plan assets		13.2
Pension plans \| Other
Employee benefit plans
Fair value of plan assets		1.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Pension plans
Employee benefit plans
Fair value of plan assets		10.5
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Pension plans \| Global equity common trust funds
Employee benefit plans
Fair value of plan assets		0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Pension plans \| Fixed income common trust funds
Employee benefit plans
Fair value of plan assets		0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Pension plans \| Commingled global fund allocation
Employee benefit plans
Fair value of plan assets		0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Pension plans \| Corporate bonds
Employee benefit plans
Fair value of plan assets		0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Pension plans \| Non-U.S. Government securities
Employee benefit plans
Fair value of plan assets		0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Pension plans \| U.S. Government securities
Employee benefit plans
Fair value of plan assets		0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Pension plans \| Short-term investments
Employee benefit plans
Fair value of plan assets		10.5
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Pension plans \| Global Equity Securities
Employee benefit plans
Fair value of plan assets		0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Pension plans \| Other
Employee benefit plans
Fair value of plan assets		0.0
Significant Observable Inputs (Level 2) \| Collateralized Securities
Employee benefit plans
Fair value of plan assets	$ 0.5	2.9
Significant Observable Inputs (Level 2) \| Pension plans
Employee benefit plans
Fair value of plan assets		413.7
Significant Observable Inputs (Level 2) \| Pension plans \| Global equity common trust funds
Employee benefit plans
Fair value of plan assets		57.6
Significant Observable Inputs (Level 2) \| Pension plans \| Fixed income common trust funds
Employee benefit plans
Fair value of plan assets		163.1
Significant Observable Inputs (Level 2) \| Pension plans \| Commingled global fund allocation
Employee benefit plans
Fair value of plan assets		80.6
Significant Observable Inputs (Level 2) \| Pension plans \| Corporate bonds
Employee benefit plans
Fair value of plan assets		29.1
Significant Observable Inputs (Level 2) \| Pension plans \| Non-U.S. Government securities
Employee benefit plans
Fair value of plan assets		39.0
Significant Observable Inputs (Level 2) \| Pension plans \| U.S. Government securities
Employee benefit plans
Fair value of plan assets		31.1
Significant Observable Inputs (Level 2) \| Pension plans \| Short-term investments
Employee benefit plans
Fair value of plan assets		0.0
Significant Observable Inputs (Level 2) \| Pension plans \| Global Equity Securities
Employee benefit plans
Fair value of plan assets		13.2
Significant Observable Inputs (Level 2) \| Pension plans \| Other
Employee benefit plans
Fair value of plan assets		0.0
Significant Unobservable Inputs (Level 3)
Employee benefit plans
Fair value of plan assets	1.0	1.0	$ 1.0
Significant Unobservable Inputs (Level 3) \| Global equity common trust funds
Employee benefit plans
Fair value of plan assets	0.0	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Fixed income common trust funds
Employee benefit plans
Fair value of plan assets	0.0	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Commingled global fund allocation
Employee benefit plans
Fair value of plan assets	0.0	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Other
Employee benefit plans
Fair value of plan assets	$ 1.0	1.0	1.0
Significant Unobservable Inputs (Level 3) \| Pension plans
Employee benefit plans
Fair value of plan assets		1.0
Significant Unobservable Inputs (Level 3) \| Pension plans \| Global equity common trust funds
Employee benefit plans
Fair value of plan assets		0.0
Significant Unobservable Inputs (Level 3) \| Pension plans \| Fixed income common trust funds
Employee benefit plans
Fair value of plan assets		0.0
Significant Unobservable Inputs (Level 3) \| Pension plans \| Commingled global fund allocation
Employee benefit plans
Fair value of plan assets		0.0
Significant Unobservable Inputs (Level 3) \| Pension plans \| Corporate bonds
Employee benefit plans
Fair value of plan assets		0.0
Significant Unobservable Inputs (Level 3) \| Pension plans \| Non-U.S. Government securities
Employee benefit plans
Fair value of plan assets		0.0
Significant Unobservable Inputs (Level 3) \| Pension plans \| U.S. Government securities
Employee benefit plans
Fair value of plan assets		0.0
Significant Unobservable Inputs (Level 3) \| Pension plans \| Short-term investments
Employee benefit plans
Fair value of plan assets		0.0
Significant Unobservable Inputs (Level 3) \| Pension plans \| Global Equity Securities
Employee benefit plans
Fair value of plan assets		0.0
Significant Unobservable Inputs (Level 3) \| Pension plans \| Other
Employee benefit plans
Fair value of plan assets		$ 1.0
United States
Employee benefit plans
Actual Allocations	100.00%	100.00%
Mid-point of Target Allocation Range	100.00%
Fair value of plan assets	$ 269.7	$ 261.9	279.2
United States \| Global equity common trust funds
Employee benefit plans
Actual Allocations	7.00%	12.00%
Mid-point of Target Allocation Range	5.00%
United States \| Fixed income common trust funds
Employee benefit plans
Actual Allocations	70.00%	44.00%
Mid-point of Target Allocation Range	65.00%
United States \| Commingled global fund allocation
Employee benefit plans
Actual Allocations	12.00%	19.00%
Mid-point of Target Allocation Range	18.00%
United States \| Corporate bonds
Employee benefit plans
Actual Allocations	1.00%	11.00%
Mid-point of Target Allocation Range	0.00%
United States \| U.S. Government securities
Employee benefit plans
Actual Allocations	9.00%	12.00%
Mid-point of Target Allocation Range	10.00%
United States \| Short-term investments
Employee benefit plans
Actual Allocations	1.00%	2.00%
Mid-point of Target Allocation Range	2.00%
Foreign Plan
Employee benefit plans
Actual Allocations	100.00%	100.00%
Mid-point of Target Allocation Range	100.00%
Fair value of plan assets	$ 183.4	$ 163.3	$ 163.5
Foreign Plan \| Global equity common trust funds
Employee benefit plans
Actual Allocations	17.00%	16.00%
Mid-point of Target Allocation Range	14.00%
Foreign Plan \| Global equities
Employee benefit plans
Actual Allocations	0.00%	8.00%
Mid-point of Target Allocation Range	0.00%
Foreign Plan \| Fixed income common trust funds
Employee benefit plans
Actual Allocations	46.00%	30.00%
Mid-point of Target Allocation Range	39.00%
Foreign Plan \| Commingled global fund allocation
Employee benefit plans
Actual Allocations	34.00%	20.00%
Mid-point of Target Allocation Range	36.00%
Foreign Plan \| Non-U.S. Government securities
Employee benefit plans
Actual Allocations	0.00%	24.00%
Mid-point of Target Allocation Range	7.00%
Foreign Plan \| Short-term investments
Employee benefit plans
Actual Allocations	3.00%	2.00%
Mid-point of Target Allocation Range	4.00%
Fair Value, Measurements, Recurring [Member]
Employee benefit plans
Fair value of plan assets	$ 453.1
Fair Value, Measurements, Recurring [Member] \| Global equity common trust funds
Employee benefit plans
Fair value of plan assets	50.6
Fair Value, Measurements, Recurring [Member] \| Global equities
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Fixed income common trust funds
Employee benefit plans
Fair value of plan assets	270.2
Fair Value, Measurements, Recurring [Member] \| Commingled global fund allocation
Employee benefit plans
Fair value of plan assets	95.1
Fair Value, Measurements, Recurring [Member] \| Corporate bonds
Employee benefit plans
Fair value of plan assets	1.6
Fair Value, Measurements, Recurring [Member] \| Non-U.S. Government securities
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| U.S. Government securities
Employee benefit plans
Fair value of plan assets	25.2
Fair Value, Measurements, Recurring [Member] \| Short-term investments
Employee benefit plans
Fair value of plan assets	9.4
Fair Value, Measurements, Recurring [Member] \| Other
Employee benefit plans
Fair value of plan assets	1.0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Employee benefit plans
Fair value of plan assets	9.4
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Global equity common trust funds
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Global equities
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fixed income common trust funds
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Commingled global fund allocation
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Corporate bonds
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Non-U.S. Government securities
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| U.S. Government securities
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Short-term investments
Employee benefit plans
Fair value of plan assets	9.4
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Other
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Observable Inputs (Level 2)
Employee benefit plans
Fair value of plan assets	442.7
Fair Value, Measurements, Recurring [Member] \| Significant Observable Inputs (Level 2) \| Global equity common trust funds
Employee benefit plans
Fair value of plan assets	50.6
Fair Value, Measurements, Recurring [Member] \| Significant Observable Inputs (Level 2) \| Global equities
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Observable Inputs (Level 2) \| Fixed income common trust funds
Employee benefit plans
Fair value of plan assets	270.2
Fair Value, Measurements, Recurring [Member] \| Significant Observable Inputs (Level 2) \| Commingled global fund allocation
Employee benefit plans
Fair value of plan assets	95.1
Fair Value, Measurements, Recurring [Member] \| Significant Observable Inputs (Level 2) \| Corporate bonds
Employee benefit plans
Fair value of plan assets	1.6
Fair Value, Measurements, Recurring [Member] \| Significant Observable Inputs (Level 2) \| Non-U.S. Government securities
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Observable Inputs (Level 2) \| U.S. Government securities
Employee benefit plans
Fair value of plan assets	25.2
Fair Value, Measurements, Recurring [Member] \| Significant Observable Inputs (Level 2) \| Short-term investments
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Observable Inputs (Level 2) \| Other
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3)
Employee benefit plans
Fair value of plan assets	1.0
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) \| Global equity common trust funds
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) \| Global equities
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) \| Fixed income common trust funds
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) \| Commingled global fund allocation
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) \| Corporate bonds
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) \| Non-U.S. Government securities
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) \| U.S. Government securities
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) \| Short-term investments
Employee benefit plans
Fair value of plan assets	0.0
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) \| Other
Employee benefit plans
Fair value of plan assets	$ 1.0