Federal Home Loan Bank and Federal Reserve Bank Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
FHLB Fixed Rate Advances, Maturities Summary [Abstract]
Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate of Amounts Due within One Year of Balance Sheet Date	2.64%
Federal Home Loan Bank, Advances, Maturities Summary, Fixed Rate, under One Year	$ 392,000
Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, One To Five Years From Balance Sheet Date	3.85%
FHLB Fixed Rate Advances, Over 1 through 5 years	$ 2,000
FHLB Fixed Rate Advances, Weighted Average Interest Rate, Due after 10 years	5.37%
FHLB Fixed Rate Advances, Due after 10 years	$ 5,000
FHLB Fixed Rate Advances, Total Amount before valuation adjustment	399,000
Valuation adjustment from acquisition accounting	523
FHLB Fixed Rate Advances, Total Amount	399,523
Federal Home Loan Bank, Advances, Activity for Year [Abstract]
FHLB Advances	399,523	$ 11,579	$ 6,493
Federal Home Loan Bank, Advances, Activity for Year, Average Balance of Agreements Outstanding	166,563	79,788	79,673
Maximum month-end balance during the year	$ 399,523	$ 317,480	$ 250,515
Weighted average rate during the year	2.29%	1.33%	0.80%
Weighted average rate at December 31	2.68%	4.08%	5.42%
FHLB Borrowing Capacity	$ 1,620,000	$ 1,430,000
Federal Reserve Bank, Advances, Activity for Year [Abstract]
Average balance during the year	14
Federal Reserve Bank borrowing capacity	$ 107,100	$ 100,100