Federal Home Loan Bank Advances and Other Borrowings - Activities in advances from the FHLB (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Activities in advances from the FHLB
Average balance outstanding	$ 290,839	$ 58,814
Maximum amount outstanding at any month-end during the year	490,148	278,000
Balance outstanding at end of year	$ 490,148	$ 278,000
Weighted average interest rate during the year	1.19%	0.59%