Pensions - Summary of Pension Assets in Three-Tier Fair Value Hierarchy for Benefit Plan (Details) - USD ($)		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Receivables		$ 300,000	$ 400,000
U.S. Benefit Plans
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		131,700,000	131,100,000	$ 128,100,000
U.S. Benefit Plans | Total
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value	[1]	131,400,000	130,700,000
U.S. Benefit Plans | Total | Cash and Cash Equivalents
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		4,200,000	5,700,000
U.S. Benefit Plans | Total | US Large Cap Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		39,700,000	36,500,000
U.S. Benefit Plans | Total | US Small and Mid Cap Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		18,500,000	16,900,000
U.S. Benefit Plans | Total | Developed International Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		19,400,000	16,300,000
U.S. Benefit Plans | Total | Emerging Markets Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		12,900,000	12,400,000
U.S. Benefit Plans | Total | Government Securities Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		6,600,000	7,100,000
U.S. Benefit Plans | Total | Asset-backed Securities Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		11,700,000	9,900,000
U.S. Benefit Plans | Total | Corporate Bonds Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		13,900,000	14,900,000
U.S. Benefit Plans | Total | Mutual Funds Other Investments
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		1,400,000	5,600,000
U.S. Benefit Plans | Total | Real Estate
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		3,100,000	5,400,000
U.S. Benefit Plans | Level 1
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		97,900,000	97,600,000
U.S. Benefit Plans | Level 1 | Cash and Cash Equivalents
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		4,200,000	5,700,000
U.S. Benefit Plans | Level 1 | US Large Cap Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		39,700,000	36,400,000
U.S. Benefit Plans | Level 1 | US Small and Mid Cap Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		18,500,000	16,900,000
U.S. Benefit Plans | Level 1 | Developed International Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		12,300,000	8,600,000
U.S. Benefit Plans | Level 1 | Emerging Markets Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		12,100,000	11,900,000
U.S. Benefit Plans | Level 1 | Government Securities Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		6,600,000	7,100,000
U.S. Benefit Plans | Level 1 | Asset-backed Securities Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 1 | Corporate Bonds Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 1 | Mutual Funds Other Investments
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		1,400,000	5,600,000
U.S. Benefit Plans | Level 1 | Real Estate
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		3,100,000	5,400,000
U.S. Benefit Plans | Level 2
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		33,500,000	33,100,000
U.S. Benefit Plans | Level 2 | Cash and Cash Equivalents
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 2 | US Large Cap Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	100,000
U.S. Benefit Plans | Level 2 | US Small and Mid Cap Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 2 | Developed International Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		7,100,000	7,700,000
U.S. Benefit Plans | Level 2 | Emerging Markets Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		800,000	500,000
U.S. Benefit Plans | Level 2 | Government Securities Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 2 | Asset-backed Securities Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		11,700,000	9,900,000
U.S. Benefit Plans | Level 2 | Corporate Bonds Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		13,900,000	14,900,000
U.S. Benefit Plans | Level 2 | Mutual Funds Other Investments
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 2 | Real Estate
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 3
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 3 | Cash and Cash Equivalents
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 3 | US Large Cap Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 3 | US Small and Mid Cap Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 3 | Developed International Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 3 | Emerging Markets Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 3 | Government Securities Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 3 | Asset-backed Securities Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 3 | Corporate Bonds Fixed Income | Fixed Income Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 3 | Mutual Funds Other Investments
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
U.S. Benefit Plans | Level 3 | Real Estate
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
Non-U.S. Benefit Plan
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		54,700,000	48,500,000	$ 54,300,000
Non-U.S. Benefit Plan | Total
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		54,700,000	48,500,000
Non-U.S. Benefit Plan | Total | Cash and Cash Equivalents
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		800,000	400,000
Non-U.S. Benefit Plan | Total | Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		41,100,000	41,900,000
Non-U.S. Benefit Plan | Total | Government Securities Fixed Income
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		3,600,000	1,300,000
Non-U.S. Benefit Plan | Total | Corporate Bonds Fixed Income
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		9,200,000	4,900,000
Non-U.S. Benefit Plan | Level 1
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		11,200,000	4,300,000
Non-U.S. Benefit Plan | Level 1 | Cash and Cash Equivalents
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		800,000	400,000
Non-U.S. Benefit Plan | Level 1 | Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
Non-U.S. Benefit Plan | Level 1 | Government Securities Fixed Income
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		3,600,000	1,300,000
Non-U.S. Benefit Plan | Level 1 | Corporate Bonds Fixed Income
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		6,800,000	2,600,000
Non-U.S. Benefit Plan | Level 2
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		43,500,000	44,200,000
Non-U.S. Benefit Plan | Level 2 | Cash and Cash Equivalents
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
Non-U.S. Benefit Plan | Level 2 | Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		41,100,000	41,900,000
Non-U.S. Benefit Plan | Level 2 | Government Securities Fixed Income
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
Non-U.S. Benefit Plan | Level 2 | Corporate Bonds Fixed Income
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		2,400,000	2,300,000
Non-U.S. Benefit Plan | Level 3
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
Non-U.S. Benefit Plan | Level 3 | Cash and Cash Equivalents
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
Non-U.S. Benefit Plan | Level 3 | Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
Non-U.S. Benefit Plan | Level 3 | Government Securities Fixed Income
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		0	0
Non-U.S. Benefit Plan | Level 3 | Corporate Bonds Fixed Income
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total assets at fair value		$ 0	$ 0

[1] Total assets at fair value in the table above exclude a net receivable of $0.3 million and $0.4 million at December 31, 2017 and 2016, respectively.