Significant Accounting Policies (Details) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014 Bank Pools	Jun. 24, 2014	Dec. 31, 2013	Sep. 30, 2013	Sep. 18, 2013	May 23, 2013	Apr. 20, 2009	Jan. 31, 2008
Accounting Policies [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		$ 250,000
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	0
Number of shares authorized to be repurchased									500,000
Stock repurchased (shares)		0
Number of remaining shares authorized to be repurchased (shares)	500,000	500,000
Common Stock, Shares, Issued	32,762,591	32,762,591	2,500,000	29,789,825	29,778,250	2,213,750
CommonStockIssuedOverAllotment			375,000			288,750
Shares Issued, Price Per Share			$ 28.00			$ 26.00
Issuance of common stock, net of issuance costs			76,200,000			53,900,000
Stock Registered Under Universal Shelf Registration							100,000,000
Preferred stock, shares authorized	200,000	200,000		200,000	200,000			200,000
Preferred stock, shares issued	0	0		0	0
Preferred stock, shares outstanding	0	0
Expense related to qualified affordable housing projects	100,000	300,000
Remaining investment in qualified affordable housing projects	$ 3,000,000	$ 3,000,000		$ 3,200,000	$ 3,300,000