Commitments and Contingencies - RCRA Compliance Matters (Details) - WRC - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Expected remaining costs under consent order	$ 4.2
Expenses related to environmental, health and safety (EHS) matters	$ 15.6	$ 17.2	$ 35.7

Amount of environmental remediation costs capitalized. These expenditures may relate to long-lived improvements in operating facilities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 25
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=39739230&loc=d3e11660-110855

Name:	us-gaap_EnvironmentalCostsRecognizedCapitalizedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration