Regulatory Capital (Details) (USD $)	6 Months Ended
Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Regulatory Capital (Textual) [Abstract]
Risk weighted assets	$ 4,000,000,000	$ 3,880,000,000	$ 3,760,000,000
Dividend pay	10,300,000
Chemical Financial Corporation [Member]
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	542,827,000	517,547,000	486,917,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	319,863,000	310,316,000	300,744,000
Actual, Ratio	13.60%	13.30%	13.00%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	492,395,000	468,565,000	439,394,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	159,931,000	155,158,000	150,372,000
Actual, Ratio	12.30%	12.10%	11.70%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Leverage Ratio:
Actual, Capital Amount	492,395,000	468,565,000	439,394,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	208,808,000	208,013,000	203,915,000
Actual, Ratio	9.40%	9.00%	8.60%
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	535,868,000	510,290,000	478,734,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	319,236,000	310,119,000	300,517,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	399,045,000	387,649,000	375,646,000
Actual, Ratio	13.40%	13.20%	12.70%
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	485,533,000	461,338,000	431,247,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	159,618,000	155,060,000	150,258,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	239,427,000	232,589,000	225,388,000
Actual, Ratio	12.20%	11.90%	11.50%
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	485,533,000	461,338,000	431,247,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	208,778,000	208,033,000	203,878,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 260,973,000	$ 260,042,000	$ 254,847,000
Actual, Ratio	9.30%	8.90%	8.50%
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 minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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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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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in 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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Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

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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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The minimum amount of Tier 1 Risk Based Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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