Note 2 - Business Combination (Details) - Acquired Loans Fair Value (Firstbank Corporation [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2014
Commercial Loans:
Loans	$ 943,662,000
Commercial and Industrial [Member] | Nonperforming Financing Receivable [Member]
Commercial Loans:
Loans	878,000
Commercial and Industrial [Member] | Performing Financing Receivable [Member]
Commercial Loans:
Loans	163,316,000
Commercial and Industrial [Member]
Commercial Loans:
Loans	164,194,000
Commercial Real Estate Portfolio Segment [Member] | Nonperforming Financing Receivable [Member]
Commercial Loans:
Loans	12,973,000
Commercial Real Estate Portfolio Segment [Member] | Performing Financing Receivable [Member]
Commercial Loans:
Loans	378,016,000
Commercial Real Estate Portfolio Segment [Member]
Commercial Loans:
Loans	390,989,000
Commercial Real Estate Construction Financing Receivable [Member] | Nonperforming Financing Receivable [Member]
Commercial Loans:
Loans	1,289,000
Commercial Real Estate Construction Financing Receivable [Member] | Performing Financing Receivable [Member]
Commercial Loans:
Loans	33,726,000
Commercial Real Estate Construction Financing Receivable [Member]
Commercial Loans:
Loans	35,015,000
Commercial Portfolio Segment [Member] | Nonperforming Financing Receivable [Member]
Commercial Loans:
Loans	15,140,000
Commercial Portfolio Segment [Member] | Performing Financing Receivable [Member]
Commercial Loans:
Loans	575,058,000
Commercial Portfolio Segment [Member]
Commercial Loans:
Loans	590,198,000
Residential Portfolio Segment [Member] | Nonperforming Financing Receivable [Member]
Commercial Loans:
Loans	9,694,000
Residential Portfolio Segment [Member] | Performing Financing Receivable [Member]
Commercial Loans:
Loans	216,653,000
Residential Portfolio Segment [Member]
Commercial Loans:
Loans	226,347,000
Consumer Installment Portfolio Segment [Member] | Nonperforming Financing Receivable [Member]
Commercial Loans:
Loans	167,000
Consumer Installment Portfolio Segment [Member] | Performing Financing Receivable [Member]
Commercial Loans:
Loans	61,657,000
Consumer Installment Portfolio Segment [Member]
Commercial Loans:
Loans	61,824,000
Consumer Home Equity Line Portfolio Segment [Member] | Nonperforming Financing Receivable [Member]
Commercial Loans:
Loans	288,000
Consumer Home Equity Line Portfolio Segment [Member] | Performing Financing Receivable [Member]
Commercial Loans:
Loans	52,054,000
Consumer Home Equity Line Portfolio Segment [Member]
Commercial Loans:
Loans	52,342,000
Consumer Construction Portfolio Segment [Member] | Nonperforming Financing Receivable [Member]
Commercial Loans:
Loans	76,000
Consumer Construction Portfolio Segment [Member] | Performing Financing Receivable [Member]
Commercial Loans:
Loans	12,875,000
Consumer Construction Portfolio Segment [Member]
Commercial Loans:
Loans	12,951,000
Consumer Portfolio Segment [Member] | Nonperforming Financing Receivable [Member]
Commercial Loans:
Loans	10,225,000
Consumer Portfolio Segment [Member] | Performing Financing Receivable [Member]
Commercial Loans:
Loans	343,239,000
Consumer Portfolio Segment [Member]
Commercial Loans:
Loans	353,464,000
Nonperforming Financing Receivable [Member]
Commercial Loans:
Loans	25,365,000
Performing Financing Receivable [Member]
Commercial Loans:
Loans	$ 918,297,000