Loans and Allowance for Loan Losses (Changes in Carrying Amount of Purchased Credit Impaired Loans and Related Accretable Yield) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Loans and Allowance for Loan Losses [Abstract]
Carrying Amount of Loans, Balance at beginning of period	$ 190,915
Carrying Amount of Loans, Balance at beginning of period	190,915	$ 225,838
Carrying Amount of Loans, Payments received, net	(69,591)	(55,194)
Carrying Amount of Loans, Accretion	17,079	20,271
Carrying Amount of Loans, Balance at end of period	153,403	190,915
Accretable Yield, Balance at beginning of period	113,686	129,488
Accretable Yield, Payments received, net	(7,412)	(11,024)
Accretable Yield, Accretion	(17,079)	(20,271)
Accretable Yield, Increase (decrease) in expected cash flows based on actual cash flow and changes in cash flow assumptions	(30,379)	5,358
Accretable Yield, Net transfers from nonaccretable difference to accretable yield	3,701	10,135
Accretable Yield, Balance at end of period	$ 62,517	$ 113,686