Investment Securities Investment Securities, Part III (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	$ 88,726
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	114,719
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis	77,765
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	4,555
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis	285,765
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Rolling Maturity [Abstract]
Available-for-sale Debt Securities, Amortized Cost Basis	581,543
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis	295,778
Available-For-Sale Securities, Debt Maturities, SIngle Maturity Date, Fair Value single maturity [Abstract]
AFS Securities, Debt Maturities, Single Maturity Date, Next Twelve Months, Fair Value	87,358
AFS Securities, Debt Maturities, Single Maturity Date, Year Two Through Five, Fair Value	114,825
AFS Securities, Debt Maturities, Single Maturity Date, Year Six Through Ten, Fair Value	78,246
AFS Securities, Debt Maturities, Single Maturity Date, After Ten Years, Fair Value	4,339
Available-for-sale Securities, Debt Maturities, Single Maturity Date	284,768
Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value	293,811
Fair Value	578,579	$ 619,848
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	39,993
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	29,339
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	0
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	0
Held-to-maturity, at amortized cost (estimated fair value of $68,457 and $73,096 at December 31, 2017 and 2016, respectively)	69,332	74,231
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Fair Value [Abstract]
Held-to-maturity Securities, Debt Maturities, Next Twelve Months, Fair Value	39,105
Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Fair Value	29,352
Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value	0
Held-to-maturity Securities, Debt Maturities, after Ten Years, Fair Value	0
Held-to-maturity Securities, Fair Value	$ 68,457	$ 73,096