Borrowings Textuals (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	May. 31, 2015	Mar. 31, 2015
Borrowings [Line Items]
Proceeds from Federal Home Loan Bank Advances	$ 50,000
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Weighted Average Interest Rate	1.30%
Federal Home Loan Bank, Advances, Weighted Average Interest Rate	1.39%
Maximum original maturity term of short-term borrowings	30 days
Long-term Federal Home Loan Bank Advances	$ 231,357	$ 181,394		$ 0
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	2,920,000
Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Two	7,100
Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Three	47,100
Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Four	67,100
Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Five	100
Federal Home Loan Bank, Advances, Maturities Summary, Floating Rate, after Five Years	110,000
Securities Sold under Agreements to Repurchase	283,383	297,199		372,236
Securities Sold Under Agreements to Repurchase, Maturities Summary, Due Remainder of Current Year	8,300
Securities Sold Under Agreements to Repurchase, Maturities, Due in Year Two	9,100
nonrevolving line of credit	$ 25,000	25,000		0
Line of Credit Facility, Interest Rate at Period End	2.39%
Subordinated Debt	$ 0	$ 18,544	$ 18,600	$ 0