Regulatory Capital (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Risk weighted assets	$ 4,360,000,000	$ 4,180,000,000	$ 4,000,000,000
Chemical Financial Corporation [Member]
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	572,503,000	552,171,000	542,827,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	348,442,000	334,140,000	319,863,000
Actual, Ratio	13.10%	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	517,716,000	499,563,000	492,395,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	174,221,000	167,070,000	159,931,000
Actual, Ratio	11.90%	12.00%	12.30%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Leverage Ratio:
Actual, Capital Amount	517,716,000	499,563,000	492,395,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	228,436,000	217,145,000	208,808,000
Actual, Ratio	9.10%	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	556,536,000	536,223,000	535,868,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	347,865,000	333,195,000	319,236,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	434,831,000	416,494,000	399,045,000
Actual, Ratio	12.80%	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	501,839,000	483,761,000	485,533,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	173,932,000	166,598,000	159,618,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	260,899,000	249,896,000	239,427,000
Actual, Ratio	11.50%	11.60%	12.20%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	6.00%	6.00%	6.00%
Leverage Ratio:
Actual, Capital Amount	501,839,000	483,761,000	485,533,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	228,126,000	216,784,000	208,778,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 285,157,000	$ 270,980,000	$ 260,973,000
Actual, Ratio	8.80%	8.90%	9.30%
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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