Securities (Unrealized Loss NOT deemed to be OTTI) (Details) $ in Thousands	Mar. 31, 2019 USD ($) holding	Dec. 31, 2018 USD ($) holding
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	162	205
Fair value, less than 12 months	$ 5,796	$ 202,901
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	(11)	(2,486)
Fair value, 12 months or longer	614,499	566,107
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	(9,492)	(16,926)
Fair value, Total	620,295	769,008
Available for Sale and Held to Maturity Securities Continuous Unrealized Loss Position Aggregate Loss	$ (9,503)	$ (19,412)
U. S. Government Agency Securities [Member]
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	3	3
Fair value, less than 12 months	$ 4,306	$ 9,960
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	(1)	(43)
Fair value, 12 months or longer	22,428	22,078
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	(46)	(396)
Fair value, Total	26,734	32,038
Available for Sale and Held to Maturity Securities Continuous Unrealized Loss Position Aggregate Loss	$ (47)	$ (439)
Agency mortgage-backed securities
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	110	144
Fair value, less than 12 months	$ 0	$ 104,616
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months		(1,363)
Fair value, 12 months or longer	246,113	222,850
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	(1,997)	(5,147)
Fair value, Total	246,113	327,466
Available for Sale and Held to Maturity Securities Continuous Unrealized Loss Position Aggregate Loss	$ (1,997)	$ (6,510)
Agency Collateralized Mortgage Obligations [Member]
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	41	48
Fair value, less than 12 months	$ 0	$ 57,871
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	0	(398)
Fair value, 12 months or longer	285,297	279,229
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	(6,139)	(9,957)
Fair value, Total	285,297	337,100
Available for Sale and Held to Maturity Securities Continuous Unrealized Loss Position Aggregate Loss	$ (6,139)	$ (10,355)
Single issuer trust preferred securities issued by banks and insurers
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	1	2
Fair value, less than 12 months	$ 1,490	$ 2,197
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	(10)	(20)
Fair value, 12 months or longer	0	0
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	0	0
Fair value, Total	1,490	2,197
Available for Sale and Held to Maturity Securities Continuous Unrealized Loss Position Aggregate Loss	$ (10)	$ (20)
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
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	0	0
Fair value, 12 months or longer	1,314	1,329
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	(346)	(349)
Fair value, Total	1,314	1,329
Available for Sale and Held to Maturity Securities Continuous Unrealized Loss Position Aggregate Loss	$ (346)	$ (349)
Small Business Administration Pooled Securities [Member]
Summary of gross unrealized losses and fair value of investments
No of holdings | holding	6	7
Fair value, less than 12 months	$ 0	$ 28,257
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for less than 12 months	0	(662)
Fair value, 12 months or longer	59,347	40,621
Unrealized loss position for available for sale and held to maturity securities in a continuous loss position for more than 12 months	(964)	(1,077)
Fair value, Total	59,347	68,878
Available for Sale and Held to Maturity Securities Continuous Unrealized Loss Position Aggregate Loss	$ (964)	$ (1,739)