Restrictions on Cash and Dividends Restrictions on Cash and Dividends (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010
Restrictions on Cash and Dividends [Abstract]
Average Balance On Deposit To Satisfy Reserve Requirements	$ 4.5	$ 6.2
Cash And Due Deposited With The Federal Reserve Bank	$ 3.1
Dividends Paid By Subsidiaries, Undistributed Net Income, Period	2 years

Dividends Paid By Subsidiaries, Undistributed Net Income, Period

No definition available.

Name:	fmer_DividendsPaidBySubsidiariesUndistributedNetIncomePeriod
Namespace Prefix:	fmer_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration