Investment Securities Held to Maturity Securities by Type (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 389,621	$ 422,096
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	5	345
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(15,693)	(4,192)
Securities held to maturity, fair value	373,933	418,249
US Government Agencies Residential Mortgage-backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	3,663	3,925
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(156)	(14)
Securities held to maturity, fair value	3,507	3,911
US Government Agency Debt Securities Commercial [Domain]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	55,726	58,249
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(2,742)	(1,394)
Securities held to maturity, fair value	52,984	56,855
Residential Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	273,972	305,126
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	10
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(11,468)	(2,552)
Securities held to maturity, fair value	262,504	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	13,413	14,056
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(427)	(71)
Securities held to maturity, fair value	12,986	13,985
Obligations of States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	42,447	40,540
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	5	335
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(895)	(161)
Securities held to maturity, fair value	41,557	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	(5)	0
Securities held to maturity, fair value	$ 395	$ 200