Investment Securities Available-for-sale (Details 1) $ in Thousands	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Available-for-sale securities in a continuous loss position, number of securities	140	157
Available-for-sale securities in a continuous loss position, less than 12 months, estimated fair value	$ 304,391	$ 361,079
Available-for-sale securities in a continuous loss position, less than 12 months, unrealized losses	3,822	5,285
Available-for-sale securities in a continuous loss position, 12 months or greater, estimated fair value	26,859	23,170
Available-for-sale securities in a continuous loss position, 12 months or greater, unrealized losses	593	619
Available-for-sale securities in a continuous loss position, estimated fair value	331,250	384,249
Available-for-sale securities in a continuous loss position, unrealized losses	$ 4,415	$ 5,904
US Government Agencies Debt Securities [Member]
Available-for-sale securities in a continuous loss position, number of securities	24	27
Available-for-sale securities in a continuous loss position, less than 12 months, estimated fair value	$ 83,448	$ 88,991
Available-for-sale securities in a continuous loss position, less than 12 months, unrealized losses	1,353	1,764
Available-for-sale securities in a continuous loss position, 12 months or greater, estimated fair value	3,381	3,768
Available-for-sale securities in a continuous loss position, 12 months or greater, unrealized losses	18	38
Available-for-sale securities in a continuous loss position, estimated fair value	86,829	92,759
Available-for-sale securities in a continuous loss position, unrealized losses	$ 1,371	$ 1,802
Residential Mortgage Backed Securities [Member]
Available-for-sale securities in a continuous loss position, number of securities	116	112
Available-for-sale securities in a continuous loss position, less than 12 months, estimated fair value	$ 220,943	$ 232,347
Available-for-sale securities in a continuous loss position, less than 12 months, unrealized losses	2,469	3,110
Available-for-sale securities in a continuous loss position, 12 months or greater, estimated fair value	23,478	19,402
Available-for-sale securities in a continuous loss position, 12 months or greater, unrealized losses	575	581
Available-for-sale securities in a continuous loss position, estimated fair value	244,421	251,749
Available-for-sale securities in a continuous loss position, unrealized losses	$ 3,044	$ 3,691
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities in a continuous loss position, number of securities		16
Available-for-sale securities in a continuous loss position, less than 12 months, estimated fair value		$ 34,743
Available-for-sale securities in a continuous loss position, less than 12 months, unrealized losses		400
Available-for-sale securities in a continuous loss position, estimated fair value		34,743
Available-for-sale securities in a continuous loss position, unrealized losses		$ 400
Corporate Debt Securities [Member]
Available-for-sale securities in a continuous loss position, number of securities		2
Available-for-sale securities in a continuous loss position, less than 12 months, estimated fair value		$ 4,998
Available-for-sale securities in a continuous loss position, less than 12 months, unrealized losses		11
Available-for-sale securities in a continuous loss position, estimated fair value		4,998
Available-for-sale securities in a continuous loss position, unrealized losses		$ 11