Borrowings Textuals (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	May 31, 2015
Borrowings [Line Items]
Proceeds from Federal Home Loan Bank Advances	$ 100,000	$ 50,000
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Weighted Average Interest Rate	1.00%	1.30%	1.00%
Federal Home Loan Bank, Advances, Weighted Average Interest Rate	1.27%		1.27%
Maximum original maturity term of short-term borrowings			30 days
Long-term Federal Home Loan Bank Advances	$ 329,320		$ 329,320	$ 181,394	$ 81,469
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	2,980,000		2,980,000
Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months	5,100		5,100
Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Two	47,100		47,100
Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Three	67,100		67,100
Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Four	100,000		100,000
Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Five	110,000		110,000
Securities Sold under Agreements to Repurchase	256,213		256,213	297,199	305,291
Securities Sold Under Agreements to Repurchase, Maturities Summary, Due Remainder of Current Year	8,100		8,100
Securities Sold Under Agreements to Repurchase, Maturities, Due in Year Two	9,200		9,200
nonrevolving line of credit	$ 25,000		$ 25,000	25,000	25,000
Line of Credit Facility, Interest Rate at Period End	2.41%		2.41%
Subordinated Debt	$ 0		$ 0	18,544	18,372	$ 18,600
Federal Home Loan Bank Advances	300,000		300,000	100,000	205,000
Federal Funds Purchased	$ 0		$ 0	$ 0	$ 22,000