Investment Securities Held to Maturity Securities by Type (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 403,019	$ 422,096
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	60	345
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(12,911)	(4,192)
Securities held to maturity, fair value	390,168	418,249
US Government Agencies Residential Mortgage-backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	3,867	3,925
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(128)	(14)
Securities held to maturity, fair value	3,739	3,911
US Government Agency Debt Securities Commercial [Domain]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	56,991	58,249
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(2,509)	(1,394)
Securities held to maturity, fair value	54,482	56,855
Residential Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	285,624	305,126
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	10
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(9,241)	(2,552)
Securities held to maturity, fair value	276,383	302,584
Obligations of U.S. Government-Sponsored Enterprises - Mortgage-Backed Securities - Commercial [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	13,659	14,056
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(369)	(71)
Securities held to maturity, fair value	13,290	13,985
Obligations of States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	42,478	40,540
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	60	335
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(655)	(161)
Securities held to maturity, fair value	41,883	40,714
Debt Security, Government, Non-US [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	400	200
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(9)	0
Securities held to maturity, fair value	$ 391	$ 200