Loans and Allowance for Loan Losses (Changes in Carrying Amount of Purchased Credit Impaired Loans and Related Accretable Yield) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Loans and Allowance for Loan Losses [Abstract]
Carrying Amount of Loans, Balance at beginning of period	$ 153,403	$ 190,915
Carrying Amount of Loans, Addition of cost recovery loans - FNBC I		15,000
Carrying Amount of Loans, Payments received, net	(21,082)	(69,591)
Carrying Amount of Loans, Accretion	8,285	17,079
Carrying Amount of Loans, Balance at end of period	140,606	153,403
Accretable Yield, Balance at beginning of period	62,517	113,686
Accretable Yield, Payments received, net	(3,215)	(7,412)
Accretable Yield, Accretion	(8,285)	(17,079)
Accretable Yield, Increase (decrease) in expected cash flows based on actual cash flow and changes in cash flow assumptions	(1,889)	(30,379)
Accretable Yield, Net transfers from nonaccretable difference to accretable yield		3,701
Accretable Yield, Balance at end of period	$ 49,128	$ 62,517