Investment Securities Available-for-sale (Details 2) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Amortized cost	$ 499,405	$ 541,364
Estimated fair value	497,672	538,108
US Government Agencies Debt Securities [Member]
One year or less, amortized cost	82,671	83,885
One year or less, estimated fair value	81,668	82,548
After one year through five years, amortized cost	55,134	20,736
After one year through five years, estimated fair value	55,281	20,897
Five years through ten years, amortized cost	9,068	2,804
Five years through ten years, estimated fair value	8,913	2,697
Residential Mortgage Backed Securities [Member]
Amortized cost, without maturity date	299,136	329,606
Estimated fair value, without maturity date	296,541	326,239
US States and Political Subdivisions Debt Securities [Member]
One year or less, amortized cost	2,891	1,056
One year or less, estimated fair value	2,952	1,070
After one year through five years, amortized cost	19,616	45,808
After one year through five years, estimated fair value	20,430	46,865
Five years through ten years, amortized cost	19,586	46,668
Five years through ten years, estimated fair value	20,317	46,839
After ten years, amortized cost	1,073	1,075
After ten years, estimated fair value	1,187	1,156
Corporate Debt Securities [Member]
After one year through five years, amortized cost	8,512	8,008
After one year through five years, estimated fair value	8,665	8,079
After ten years, amortized cost	1,500	1,500
After ten years, estimated fair value	1,500	1,500
Investment Securities [Member]
Amortized cost, without maturity date	218	218
Estimated fair value, without maturity date	$ 218	$ 218