Regulatory Capital (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Risk weighted assets	$ 4,510,000,000	$ 4,180,000,000	$ 4,030,000,000
Chemical Financial Corporation [Member]
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	638,786,000	552,171,000	549,388,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	361,199,000	334,140,000	322,212,000
Actual, Ratio	14.20%	13.20%	13.60%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	582,039,000	499,563,000	498,618,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	180,600,000	167,070,000	161,106,000
Actual, Ratio	12.90%	12.00%	12.40%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Leverage Ratio:
Actual, Capital Amount	582,039,000	499,563,000	498,618,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	232,972,000	217,145,000	211,670,000
Actual, Ratio	10.00%	9.20%	9.40%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Chemical Bank [Member]
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	568,626,000	536,223,000	537,467,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	360,617,000	333,195,000	321,585,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	450,771,000	416,494,000	401,982,000
Actual, Ratio	12.60%	12.90%	13.40%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%	8.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	10.00%	10.00%	10.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	511,969,000	483,761,000	486,794,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	180,309,000	166,598,000	160,793,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	270,463,000	249,896,000	241,189,000
Actual, Ratio	11.40%	11.60%	12.10%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	6.00%	6.00%	6.00%
Leverage Ratio:
Actual, Capital Amount	511,969,000	483,761,000	486,794,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	232,828,000	216,784,000	211,452,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 291,034,000	$ 270,980,000	$ 264,315,000
Actual, Ratio	8.80%	8.90%	9.20%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	5.00%	5.00%	5.00%

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The amount of total capital as defined in the regulations.

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The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action.

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Total Capital divided by risk weighted assets as defined in the regulations.

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Amount of risk-weighted assets as calculated in accordance with U.S. Federal regulatory capital standards.

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Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

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Tier 1 Risk Based Capital as defined in the regulations.

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