Financial Instruments With Off-Balance Sheet Risk, Contingencies and Concentration of Credit Risk (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Standby Letters of Credit
Loss Contingencies [Line Items]
Commitments and obligations, liability outstanding	$ 21.8	$ 17.7
Commitments to Extend Credit
Loss Contingencies [Line Items]
Commitments and obligations, liability outstanding	$ 829.1	$ 748.3

The face amount of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

No definition available.

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