Investment Securities Schedule of Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Due within 1 year	$ 85
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	85
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	5	$ 345
Debt Securities, Held-to-maturity	389,621	422,096
Securities held to maturity, fair value	373,933	$ 418,249
Due after 1 but within 5 years	3,814
Due after 5 but within 10 years	37,329
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	36,491
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	3,778
Due after 10 years	1,619
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	1,598
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost	42,847
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value	41,952
Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Amortized Cost	346,774
Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Fair Value	331,981
US Government Agencies Residential Mortgage-backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	59,400
Securities held to maturity, fair value	56,500
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	287,400
Securities held to maturity, fair value	$ 275,500