Loans (Summary of Purchased Impaired and Nonimpaired Loans Acquired) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Impaired Purchased Loans	$ 4,463	$ 7,716
Non Impaired Purchased Loans	926,216	775,581
Total Purchased Loans	930,679	783,297
Commercial | Commercial
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Impaired Purchased Loans	2,198	0
Non Impaired Purchased Loans	99,082	159,393
Total Purchased Loans	101,280	159,393
Commercial | Commercial real estate
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Impaired Purchased Loans	2,079	7,716
Non Impaired Purchased Loans	622,117	494,010
Total Purchased Loans	624,196	501,726
Agricultural and agricultural real estate
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Impaired Purchased Loans	0	0
Non Impaired Purchased Loans	181	2,985
Total Purchased Loans	181	2,985
Residential real estate
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Impaired Purchased Loans	186	0
Non Impaired Purchased Loans	157,468	85,549
Total Purchased Loans	157,654	85,549
Consumer
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Impaired Purchased Loans	0	0
Non Impaired Purchased Loans	47,368	33,644
Total Purchased Loans	$ 47,368	$ 33,644