Retirement Plans (Fair Value of Plan Assets by Fair Value Level) (Details) - Pension Plan - USD ($)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 132,751,000	$ 126,930,000	$ 130,775,000
Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	132,751,000	126,930,000
Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	130,442,000	120,561,000
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,309,000	6,369,000
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Cash | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,825,000	354,000
Cash | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,825,000	354,000
Cash | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Cash | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large- and mid-cap stocks
Defined Benefit Plan Disclosure [Line Items]
Minimum market capitalization for investments	3,000,000,000
U.S. large- and mid-cap stocks | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55,389,000	55,709,000
U.S. large- and mid-cap stocks | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55,389,000	55,709,000
U.S. large- and mid-cap stocks | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large- and mid-cap stocks | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small-cap mutual funds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,687,000	4,749,000
U.S. small-cap mutual funds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,687,000	4,749,000
U.S. small-cap mutual funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small-cap mutual funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International large-cap mutual funds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,701,000	14,124,000
International large-cap mutual funds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,701,000	14,124,000
International large-cap mutual funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International large-cap mutual funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Emerging markets mutual funds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,147,000	4,886,000
Emerging markets mutual funds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,147,000	4,886,000
Emerging markets mutual funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Emerging markets mutual funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Chemical Financial Corporation common stock | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,412,000	7,219,000
Chemical Financial Corporation common stock | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,412,000	7,219,000
Chemical Financial Corporation common stock | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Chemical Financial Corporation common stock | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. Treasury and government sponsored agency bonds and notes | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	806,000	2,815,000
U.S. Treasury and government sponsored agency bonds and notes | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. Treasury and government sponsored agency bonds and notes | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	806,000	2,815,000
U.S. Treasury and government sponsored agency bonds and notes | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Corporate bonds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,503,000	3,554,000
Corporate bonds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Corporate bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,503,000	3,554,000
Corporate bonds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	36,220,000	33,424,000
Mutual funds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	36,220,000	33,424,000
Mutual funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	61,000	96,000
Other | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	61,000	96,000
Other | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0