Federal Funds Purchased and Securities Sold Under Agreements to Repurchase (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Short-term Debt [Line Items]
Federal Funds Purchased	$ 80,000	$ 0	$ 0
Securities Sold under Agreements to Repurchase	59,624	58,215	30,496
Available-for-sale Securities Pledged as Collateral	182,700	187,400
Federal Funds Lines of Credit, Amount of Available Unused Funds	485,000	565,000
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Short-term Debt, Maximum Month-end Outstanding Amount	180,000	102,000	75,000
Short-term Debt, Average Outstanding Amount	$ 29,542	$ 10,008	$ 1,671
Short-term Debt, Weighted Average Interest Rate	0.75%	0.00%	0.00%
Debt Instrument, Interest Rate During Period	0.54%	0.31%	0.33%
Securities Sold under Agreements to Repurchase [Member]
Short-term Debt [Line Items]
Short-term Debt, Maximum Month-end Outstanding Amount	$ 77,466	$ 75,313	$ 154,448
Short-term Debt, Average Outstanding Amount	$ 66,282	$ 64,320	$ 108,191
Short-term Debt, Weighted Average Interest Rate	0.05%	0.05%	0.05%
Debt Instrument, Interest Rate During Period	0.05%	0.05%	0.05%