Loans (Carrying amount loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Loans covered by loss share agreement (carrying amount) [Line Items]
Impaired Purchased Loans	$ 3,688	$ 4,463
Non Impaired Purchased Loans	1,699,483	926,216
Total Purchased Loans	1,703,171	930,679
Commercial | Commercial
Loans covered by loss share agreement (carrying amount) [Line Items]
Impaired Purchased Loans	968	2,198
Non Impaired Purchased Loans	270,241	99,082
Total Purchased Loans	271,209	101,280
Commercial | Commercial real estate
Loans covered by loss share agreement (carrying amount) [Line Items]
Impaired Purchased Loans	2,509	2,079
Non Impaired Purchased Loans	1,181,333	622,117
Total Purchased Loans	1,183,842	624,196
Agricultural and agricultural real estate
Loans covered by loss share agreement (carrying amount) [Line Items]
Impaired Purchased Loans	0	0
Non Impaired Purchased Loans	1,251	181
Total Purchased Loans	1,251	181
Residential real estate
Loans covered by loss share agreement (carrying amount) [Line Items]
Impaired Purchased Loans	211	186
Non Impaired Purchased Loans	184,167	157,468
Total Purchased Loans	184,378	157,654
Consumer
Loans covered by loss share agreement (carrying amount) [Line Items]
Impaired Purchased Loans	0	0
Non Impaired Purchased Loans	62,491	47,368
Total Purchased Loans	$ 62,491	$ 47,368