Retirement Plans (Textual) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) employee shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)	Jun. 30, 2015	Jun. 24, 2014 shares	Sep. 18, 2013 shares
Defined Benefit Plan Disclosure [Line Items]
Percentage of eligible pay contribution to certain employees	4.00%
Common Stock, Shares Held by Plan | shares	(38,167,861)	(32,774,420)			(2,500,000)	(2,213,750)
Dividends paid	$ 36,918	$ 29,528	$ 24,521
Multiemployer Plan, Period Contributions	100
Multiemployer Plan Minimum Funding Status				80.00%
Multiemployer Plan, Participating Company, Allocation of Plan Assets	3,700
Multiemployer Plan, Participating Company, Allocation of Plan Liabilities	$ 2,600
Multiemployer Plan, Company's Asset Participation Level				5.00%
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Maximum years of vested service for calculation of retirement benefits	30 years
Years of employees highest average salary for calculation of retirement benefits	5 years
Defined Benefit Plan, Number of Employees Covered | employee	161
Number of years preceding retirement for calculation of retirement benefits	10 years
Maximum years of service for which pension benefits calculation is based upon vested service and average five years of salary	15 years
Maximum total years of age and years of service for which pension benefits calculation is based upon vested service and average five years of salary	65 years
Pension Plan expense	$ 1,575	(45)	1,725
Employer contributions	$ 0	$ 0	$ 15,000
Discount rate used in determining benefit obligation	4.55%	4.15%	5.00%
Pension plan actual asset allocations	100.00%	100.00%
Projected benefit obligation	$ 119,873	$ 129,160	$ 105,914
Accumulated benefit obligation	$ 109,583	$ 121,826
Pension Plan [Member] | Equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range - minimum	40.00%
Target plan asset allocations range - maximum	70.00%
Pension plan actual asset allocations	68.00%	68.00%
Pension Plan [Member] | Debt securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range - minimum	20.00%
Target plan asset allocations range - maximum	60.00%
Pension plan actual asset allocations	31.00%	30.00%
Pension Plan [Member] | Other securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range - minimum	0.00%
Target plan asset allocations range - maximum	10.00%
Pension plan actual asset allocations	1.00%	2.00%
Pension Plan [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Common Stock, Shares Held by Plan | shares	(210,663)
Fair value of common stock	$ 7,200	$ 6,500
Pension plan actual asset allocations	5.70%	4.90%
Supplemental Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of employees covered by the pension plan | employee	1
Discount rate used in determining benefit obligation	4.51%	4.07%	4.87%
Projected benefit obligation	$ 2,200	$ 2,100
Accumulated benefit obligation	1,800	2,000
Supplemental Plan expense	400	300	$ 200
Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Plan expense	278	186	$ 431
Employer contributions	$ 241	$ 247
Discount rate used in determining benefit obligation	4.23%	3.75%	4.27%
Expected health care cost trend rate assumed for 2014	7.50%
Expected ultimate health care cost trend rate in 2020	5.00%
Projected benefit obligation	$ 3,247	$ 3,702	$ 3,477
Accumulated benefit obligation	$ 3,247	3,702
Minimum retirement age (years)	50 years
Maximum benefit age of spouse (years)	65 years
Minimum retirement age with twenty-five years of service to be eligible for postretirement benefits (years)	60 years
Minimum years of service for retirees at age sixty to be eligible for postretirement benefits (years)	25 years
Chemical Financial Corporation [Member] | Pension Plan [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Dividends paid	$ 200	$ 180