Balance Sheet Offsetting (Repos - by maturity date and collateral type) (Details 1) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	$ 504,293	$ 505,293
Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	402,547	312,876
Debt Securities Issued by States and Political Subdivisions
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	3,488	3,790
Mortgage-Backed Securities: Residential - Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	97,431	101,256
Mortgage-Backed Securities: Residential - U.S. Government-Sponsored Enterprises
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	827	87,371
Maturity Up To 90 Days [Member]
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	1,993	2,703
Maturity Up To 90 Days [Member] | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	0
Maturity Up To 90 Days [Member] | Debt Securities Issued by States and Political Subdivisions
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	1,188	1,200
Maturity Up To 90 Days [Member] | Mortgage-Backed Securities: Residential - Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	805	1,503
Maturity Up To 90 Days [Member] | Mortgage-Backed Securities: Residential - U.S. Government-Sponsored Enterprises
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	0
Maturity 91 To 365 Days [Member]
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	2,300	2,590
Maturity 91 To 365 Days [Member] | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	0
Maturity 91 To 365 Days [Member] | Debt Securities Issued by States and Political Subdivisions
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	2,300	2,590
Maturity 91 To 365 Days [Member] | Mortgage-Backed Securities: Residential - Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	0
Maturity 91 To 365 Days [Member] | Mortgage-Backed Securities: Residential - U.S. Government-Sponsored Enterprises
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	0
Maturity 1 To 3 Years [Member]
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	275,000	150,000
Maturity 1 To 3 Years [Member] | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	205,002	110,392
Maturity 1 To 3 Years [Member] | Debt Securities Issued by States and Political Subdivisions
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	0
Maturity 1 To 3 Years [Member] | Mortgage-Backed Securities: Residential - Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	69,171	18,793
Maturity 1 To 3 Years [Member] | Mortgage-Backed Securities: Residential - U.S. Government-Sponsored Enterprises
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	827	20,815
Maturity After 3 Years [Member]
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	225,000	350,000
Maturity After 3 Years [Member] | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	197,545	202,484
Maturity After 3 Years [Member] | Debt Securities Issued by States and Political Subdivisions
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	0
Maturity After 3 Years [Member] | Mortgage-Backed Securities: Residential - Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	27,455	80,960
Maturity After 3 Years [Member] | Mortgage-Backed Securities: Residential - U.S. Government-Sponsored Enterprises
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	$ 0	$ 66,556