Summary of Significant Accounting Policies (Allowance of Loan Losses) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Accounting Policies [Abstract]
Minimum non-performing substandard loans outstanding for allowance for credit losses	$ 0.3
Minimum non-performing substandard doubtful loans outstanding for allowance for credit losses	$ 0.1

Minimum Non Performing Substandard Doubtful Loans Outstanding For Allowance For Credit Losses.

No definition available.

Name:	fmer_MinimumNonPerformingSubstandardDoubtfulLoansOutstandingForAllowanceForCreditLosses
Namespace Prefix:	fmer_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant