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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.

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