Investment Securities Available-for-Sale (Details 2) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortized cost	$ 557,744	$ 541,364
Estimated fair value	556,026	538,108
US Agency Securities [Member]
One year or less, amortized cost	90,495	83,885
One year or less, estimated fair value	89,503	82,548
After one year through five years, amortized cost	74,481	20,736
After one year through five years, estimated fair value	74,433	20,897
Five years through ten years, amortized cost	14,124	2,804
Five years through ten years, estimated fair value	13,982	2,697
Residential Mortgage Backed Securities [Member]
Amortized cost, without maturity date	303,822	329,606
Estimated fair value, without maturity date	301,526	326,239
Municipal Bonds [Member]
One year or less, amortized cost	2,537	1,056
One year or less, estimated fair value	2,586	1,070
After one year through five years, amortized cost	21,116	45,808
After one year through five years, estimated fair value	21,875	46,865
Five years through ten years, amortized cost	36,868	46,668
Five years through ten years, estimated fair value	37,493	46,839
After ten years, amortized cost	1,072	1,075
After ten years, estimated fair value	1,193	1,156
Corporate Bonds [Member]
After one year through five years, amortized cost	11,511	8,008
After one year through five years, estimated fair value	11,717	8,079
After ten years, amortized cost	1,500	1,500
After ten years, estimated fair value	1,500	1,500
Other Equity Investments [Member]
Amortized cost, without maturity date	218	218
Estimated fair value, without maturity date	$ 218	$ 218