Commitments and Contingent Liabilities - Financial Assurances (Details) $ in Millions	Sep. 30, 2018 USD ($)
Financial Guarantee
Financial assurances
Gross financial assurances issued and outstanding	$ 147.8
Surety Bonds
Financial assurances
Gross financial assurances issued and outstanding	67.8
Standby Letters of Credit
Financial assurances
Gross financial assurances issued and outstanding	$ 80.0

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82913245&loc=d3e12069-110248

Name:	us-gaap_GuaranteeObligationsCurrentCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant