Investment Securities, Available-for-sale Securities, Maturities (Details) $ in Thousands	Mar. 31, 2018 USD ($)
Amortized Cost [Abstract]
Due in one year or less	$ 30,717
Due in one year through five years	150,597
Due after five years through ten years	10,094
Amortized Cost	574,983
Fair Value [Abstract]
Due in one year or less	30,617
Due in one year through five years	147,053
Due after five years through ten years	10,094
Fair Value	559,083
Mortgage-Backed Securities and Collateralized Mortgage Obligations-Residential [Member]
Amortized Cost [Abstract]
Securities, amortized cost	307,679
Fair Value [Abstract]
Securities, fair value	297,633
Small Business Administration-Guaranteed Participation Securities [Member]
Amortized Cost [Abstract]
Securities, amortized cost	66,153
Fair Value [Abstract]
Securities, fair value	64,113
Mortgage-Backed Securities and Collateralized Mortgage Obligations-Commercial [Member]
Amortized Cost [Abstract]
Securities, amortized cost	9,743
Fair Value [Abstract]
Securities, fair value	$ 9,573