(Schedule of Net Funded Status) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	$ 354,402	$ 307,739
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, ending balance	257,355
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected Benefit Obligation, Beginning Balance	308,834	259,428
Service cost	728	2,339	7,194
Interest cost	14,337	12,814	11,862
Plan amendments	0	3,927
Participant contributions	0	0
actuarial gains/losses and changes in assumptions	50,115	(35,984)
Benefits paid	(18,372)	19,172
Projected Benefit Obligation, Ending Balance	355,642	308,834	259,428
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	257,510	174,385
Citizens acquisition	0	68,304
Actual return on plan assets	16,663	30,298
Participant contributions	0	0
Employer Contributions	1,554	3,695
Benefits paid	(18,372)	19,172
Fair value of plan assets, ending balance	257,355	257,510	174,385
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded Status	98,287	51,324
Amounts recognized in AOCI before income taxes:
Prior service cost (credit)	(2,587)	(5,121)
Net actuarial loss	99,715	53,061
Amount recognized in AOCI	102,302	58,182
Pension Benefits \| Citizens Republic Bancorp
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected Benefit Obligation, Ending Balance	0	85,483
Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected Benefit Obligation, Beginning Balance	15,544	14,771
Service cost	65	99	77
Interest cost	655	563	697
Plan amendments	(1,979)	0
Participant contributions	1,851	1,538
actuarial gains/losses and changes in assumptions	2,046	(682)
Benefits paid	(3,018)	2,808
Projected Benefit Obligation, Ending Balance	15,164	15,544	14,771
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	0	0
Citizens acquisition	0	0
Actual return on plan assets	0	0
Participant contributions	1,851	1,538
Employer Contributions	1,167	1,270
Benefits paid	(3,018)	2,808
Fair value of plan assets, ending balance	0	0	0
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded Status	15,164	15,544
Amounts recognized in AOCI before income taxes:
Prior service cost (credit)	(5,370)	3,858
Net actuarial loss	5,138	3,329
Amount recognized in AOCI	232	(529)
Postretirement Benefits \| Citizens Republic Bancorp
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected Benefit Obligation, Ending Balance	$ 0	$ 2,062

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For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.

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The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable.

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Amount before tax, after reclassification adjustments, of actuarial gain (loss) that has not been recognized in the income statement.

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Amount before tax, after reclassification adjustments, of prior service cost (credit) that has not been recognized in the income statement.

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1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

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The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

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The amount of increase in the benefit obligation attributed to business combinations.

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The increase in the fair value of plan assets from contributions made by the employer.

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The amount of contributions made by plan participants. This item represents a periodic increase to the plan obligation and an increase to plan assets.

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Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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The funded status is measured as the difference between the fair value of plan assets and the benefit obligation. Will normally be the same as the net Defined Benefit Plan, Amounts Recognized in Balance Sheet, Total.

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The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The amount of increase or decrease due to a change in the terms of an existing plan or the initiation of a new plan. A plan amendment may increase or decrease benefits, including those attributed to years of service already rendered.

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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This represents the entire liability recognized in the balance sheet that is associated with the defined benefit plans.

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