Significant Accounting Policies (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2012 Pools Bank	Dec. 31, 2011	Jun. 30, 2011	Apr. 20, 2009	Jan. 31, 2008
Significant Accounting Policies (Textual) [Abstract]
Number of banks through which company operates	1
Number of regional banking units Chemical Bank operates through	4
Number of minimum days when principal or interest is past due is placed in nonaccrual category	90 days
Number of minimum days in real estate residential loan when principal or interest is past due is placed in nonaccrual category	120 days
Time period in which payments receive consistently and loans are returned to accrual status	6 months
Number of pools of aggregate acquired loans based upon common risk characteristics	14
Time period sustained for payment history of principal and interest payments to move them to performing status	6 months
Time period of real estate residential troubled debt restructurings reducing borrower's monthly payments by decreasing the interest rate charged on the loan	24 months
Minimum number of days past due as to interest or principal payments in accruing loans moves to nonperforming loans	90 days
Minimum amount of loan reviewed for detailed credit quality	$ 0.25
Revised time period for historical loan loss experience	5 years
Minimum percentage of tax benefit is recognized for the amount likely to be realized	50.00%
Reserve for contingent income tax liabilities recorded	$ 0	$ 0	$ 0
Number of shares authorized to be repurchased					500,000
Shares repurchased during the period	0
Number of remaining shares authorized to be repurchased	500,000
Preferred stock, shares authorized	200,000	200,000	200,000	200,000
Preferred stock, shares issued	0	0	0
Preferred stock, shares outstanding	0