Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Expenses relating to investigation	$ 2.9	$ 1.3

Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

No definition available.

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