Fair Value of Financial Instruments Recurring basis (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Investments
Total held-to-maturity securities	$ 43,227	$ 45,853
Total available-for-sale securities	777,940	784,701
Recurring Basis
Investments
Total available-for-sale securities	777,940	784,701
U.S. government sponsored agencies
Investments
Total available-for-sale securities	1,000	2,966
U.S. government sponsored agencies | Recurring Basis
Investments
Total available-for-sale securities	1,000	2,966
States and political subdivisions
Investments
Total held-to-maturity securities	4,041	4,221
Total available-for-sale securities	117,230	114,726
States and political subdivisions | Recurring Basis
Investments
Total available-for-sale securities	117,230	114,726
Residential mortgage-backed securities
Investments
Total held-to-maturity securities	33,762	35,196
Total available-for-sale securities	626,567	632,293
Residential mortgage-backed securities | Recurring Basis
Investments
Total available-for-sale securities	626,567	632,293
Commercial mortgage-backed securities
Investments
Total held-to-maturity securities	5,424	6,436
Total available-for-sale securities	19,291	23,845
Commercial mortgage-backed securities | Recurring Basis
Investments
Total available-for-sale securities	19,291	23,845
Bank-issued trust preferred securities
Investments
Total available-for-sale securities	4,899	4,635
Bank-issued trust preferred securities | Recurring Basis
Investments
Total available-for-sale securities	4,899	4,635
Equity securities
Investments
Total available-for-sale securities	8,953	6,236
Equity securities | Recurring Basis
Investments
Total available-for-sale securities	8,953	6,236
Quoted Prices in Active Markets for Identical Assets (Level 1)
Investments
Total held-to-maturity securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Recurring Basis
Investments
Total available-for-sale securities	8,734	6,024
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. government sponsored agencies | Recurring Basis
Investments
Total available-for-sale securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | States and political subdivisions
Investments
Total held-to-maturity securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | States and political subdivisions | Recurring Basis
Investments
Total available-for-sale securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Residential mortgage-backed securities
Investments
Total held-to-maturity securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Residential mortgage-backed securities | Recurring Basis
Investments
Total available-for-sale securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial mortgage-backed securities
Investments
Total held-to-maturity securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial mortgage-backed securities | Recurring Basis
Investments
Total available-for-sale securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Bank-issued trust preferred securities | Recurring Basis
Investments
Total available-for-sale securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities | Recurring Basis
Investments
Total available-for-sale securities	8,734	6,024
Significant Other Observable Inputs (Level 2)
Investments
Total held-to-maturity securities	43,227	45,853
Significant Other Observable Inputs (Level 2) | Recurring Basis
Investments
Total available-for-sale securities	769,206	778,677
Significant Other Observable Inputs (Level 2) | U.S. government sponsored agencies | Recurring Basis
Investments
Total available-for-sale securities	1,000	2,966
Significant Other Observable Inputs (Level 2) | States and political subdivisions
Investments
Total held-to-maturity securities	4,041	4,221
Significant Other Observable Inputs (Level 2) | States and political subdivisions | Recurring Basis
Investments
Total available-for-sale securities	117,230	114,726
Significant Other Observable Inputs (Level 2) | Residential mortgage-backed securities
Investments
Total held-to-maturity securities	33,762	35,196
Significant Other Observable Inputs (Level 2) | Residential mortgage-backed securities | Recurring Basis
Investments
Total available-for-sale securities	626,567	632,293
Significant Other Observable Inputs (Level 2) | Commercial mortgage-backed securities
Investments
Total held-to-maturity securities	5,424	6,436
Significant Other Observable Inputs (Level 2) | Commercial mortgage-backed securities | Recurring Basis
Investments
Total available-for-sale securities	19,291	23,845
Significant Other Observable Inputs (Level 2) | Bank-issued trust preferred securities | Recurring Basis
Investments
Total available-for-sale securities	4,899	4,635
Significant Other Observable Inputs (Level 2) | Equity securities | Recurring Basis
Investments
Total available-for-sale securities	219	212
Significant Unobservable Inputs (Level 3)
Investments
Total held-to-maturity securities	0	0
Significant Unobservable Inputs (Level 3) | Recurring Basis
Investments
Total available-for-sale securities	0	0
Significant Unobservable Inputs (Level 3) | U.S. government sponsored agencies | Recurring Basis
Investments
Total available-for-sale securities	0	0
Significant Unobservable Inputs (Level 3) | States and political subdivisions
Investments
Total held-to-maturity securities	0	0
Significant Unobservable Inputs (Level 3) | States and political subdivisions | Recurring Basis
Investments
Total available-for-sale securities	0	0
Significant Unobservable Inputs (Level 3) | Residential mortgage-backed securities
Investments
Total held-to-maturity securities	0	0
Significant Unobservable Inputs (Level 3) | Residential mortgage-backed securities | Recurring Basis
Investments
Total available-for-sale securities	0	0
Significant Unobservable Inputs (Level 3) | Commercial mortgage-backed securities
Investments
Total held-to-maturity securities	0	0
Significant Unobservable Inputs (Level 3) | Commercial mortgage-backed securities | Recurring Basis
Investments
Total available-for-sale securities	0	0
Significant Unobservable Inputs (Level 3) | Bank-issued trust preferred securities | Recurring Basis
Investments
Total available-for-sale securities	0	0
Significant Unobservable Inputs (Level 3) | Equity securities | Recurring Basis
Investments
Total available-for-sale securities	$ 0	$ 0