Intangible Assets and Goodwill (Intangibles Subject to Amortization) (Details) - USD ($) $ in Thousands  | 
Mar. 31, 2018  | 
Dec. 31, 2017  | 
|---|---|---|
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross carrying amount | $ 591,587 | |
| Accumulated amortization | (47,172) | |
| Net carrying amount | 544,415 | $ 4,237 | 
| Customer relationships | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross carrying amount | 483,267 | |
| Accumulated amortization | (26,462) | |
| Net carrying amount | 456,805 | |
| Other amortizable intangibles | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross carrying amount | 108,320 | |
| Accumulated amortization | (20,710) | |
| Net carrying amount | $ 87,610 | 
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- Definition Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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- Definition Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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