Commitments and Contingent Liabilities - Contingencies (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)
Commitments and Contingent Liabilities
Amount paid to settlement fund	$ 4.1

Amount awarded to other party in judgment or settlement of litigation.

No definition available.

Name:	us-gaap_LitigationSettlementAmountAwardedToOtherParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration