Unrealized Losses (Details 4) $ in Thousands	Dec. 31, 2018 USD ($) holding	Dec. 31, 2017 USD ($) holding
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	205	163
Fair value, less than 12 months	$ 202,901	$ 475,739
Fair value, 12 months or longer	566,107	193,298
Fair value, Total	769,008	669,037
Unrealized losses, Total	(19,412)	(10,384)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	(2,486)	(3,465)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	$ (16,926)	$ (6,919)
US Government Agencies Debt Securities [Member]
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	3	4
Fair value, less than 12 months	$ 9,960	$ 24,343
Fair value, 12 months or longer	22,078	0
Fair value, Total	32,038	24,343
Unrealized losses, Total	(439)	(131)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	(43)	(131)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	$ (396)	$ 0
Agency mortgage-backed securities [Member]
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	144	84
Fair value, less than 12 months	$ 104,616	$ 235,411
Fair value, 12 months or longer	222,850	14,886
Fair value, Total	327,466	250,297
Unrealized losses, Total	(6,510)	(1,803)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	(1,363)	(1,493)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	$ (5,147)	$ (310)
Agency collateralized mortgage obligations [Member]
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	48	42
Fair value, less than 12 months	$ 57,871	$ 178,142
Fair value, 12 months or longer	279,229	159,506
Fair value, Total	337,100	337,648
Unrealized losses, Total	(10,355)	(7,151)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	(398)	(1,579)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	$ (9,957)	$ (5,572)
Single issuer trust preferred securities issued by banks and insurers
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	2
Fair value, less than 12 months	$ 2,197
Fair value, 12 months or longer	0
Fair value, Total	2,197
Unrealized losses, Total	(20)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	(20)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	$ 0
Pooled trust preferred securities issued by banks and insurers
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	1	1
Fair value, less than 12 months	$ 0	$ 0
Fair value, 12 months or longer	1,329	1,640
Fair value, Total	1,329	1,640
Unrealized losses, Total	(349)	(539)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	0	0
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	$ (349)	$ (539)
Small Business Administration Pooled Securities [Member]
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	7	4
Fair value, less than 12 months	$ 28,257	$ 34,553
Fair value, 12 months or longer	40,621	9,647
Fair value, Total	68,878	44,200
Unrealized losses, Total	(1,739)	(318)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	(662)	(223)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	$ (1,077)	$ (95)
Marketable securities [Member]
Summary of gross unrealized losses and fair value of investments
No of holdings | holding		28
Fair value, less than 12 months		$ 3,290
Fair value, 12 months or longer		7,619
Fair value, Total		10,909
Unrealized losses, Total		(442)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months		(39)
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months		$ (403)