Repurchase Agreements (Details) - Securities Sold under Agreements to Repurchase [Member] - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	$ 250,983	$ 243,814
Asset Pledged as Collateral [Member]
Financial Instruments Pledged as Collateral [Abstract]
Carrying value of investment securities available-for-sale pledged as collateral under repurchase agreements	289,500	295,400
Overnight and Continuous [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	117,569	100,937
Up to 30 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	72,000	0
30-90 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	0	22,000
Greater Than 90 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	61,414	120,877
U.S. Treasury and Government Agencies [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	118,648	109,595
U.S. Treasury and Government Agencies [Member] | Overnight and Continuous [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	42,375	24,957
U.S. Treasury and Government Agencies [Member] | Up to 30 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	41,540	0
U.S. Treasury and Government Agencies [Member] | 30-90 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	0	16,771
U.S. Treasury and Government Agencies [Member] | Greater Than 90 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	34,733	67,867
State and Political Subdivisions [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	75,087	75,348
State and Political Subdivisions [Member] | Overnight and Continuous [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	61,820	62,620
State and Political Subdivisions [Member] | Up to 30 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	5,961	0
State and Political Subdivisions [Member] | 30-90 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	0	567
State and Political Subdivisions [Member] | Greater Than 90 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	7,306	12,161
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	57,248	58,871
U.S. Government Sponsored Agency Mortgage-backed Securities [Member] | Overnight and Continuous [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	13,374	13,360
U.S. Government Sponsored Agency Mortgage-backed Securities [Member] | Up to 30 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	24,499	0
U.S. Government Sponsored Agency Mortgage-backed Securities [Member] | 30-90 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	0	4,662
U.S. Government Sponsored Agency Mortgage-backed Securities [Member] | Greater Than 90 Days [Member]
Remaining contractual maturity of securities sold under agreements to repurchase by class of collateral pledged [Abstract]
Repurchase agreements and repurchase-to-maturity transactions	$ 19,375	$ 40,849