Investment Securities, Available-for-sale Securities, Maturities (Details) $ in Thousands	Sep. 30, 2017 USD ($)
Amortized Cost [Abstract]
Due in one year or less	$ 50,331
Due in one year through five years	106,105
Due after five years through ten years	10,201
Due after ten years	0
Amortized Cost	586,200
Fair Value [Abstract]
Due in one year or less	50,283
Due in one year through five years	104,749
Due after five years through ten years	10,190
Due after ten years	0
Fair Value	580,395
Mortgage-Backed Securities and Collateralized Mortgage Obligations-Residential [Member]
Amortized Cost [Abstract]
Securities, amortized cost	338,519
Fair Value [Abstract]
Securities, fair value	335,531
Small Business Administration-Guaranteed Participation Securities [Member]
Amortized Cost [Abstract]
Securities, amortized cost	71,169
Fair Value [Abstract]
Securities, fair value	69,818
Mortgage-Backed Securities and Collateralized Mortgage Obligations-Commercial [Member]
Amortized Cost [Abstract]
Securities, amortized cost	9,875
Fair Value [Abstract]
Securities, fair value	$ 9,824