Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale Securities [Abstract]
Amortized cost	$ 379,125	$ 354,924	[1]
Gross unrealized gains	1,367	1,282
Gross unrealized losses	4,563	6,166
Total	375,929	350,040	[1]
Held-to-maturity Securities [Abstract]
Amortized cost	152,670	142,461
Gross unrealized gains	283	116
Gross unrealized losses	1,018	1,702
Total	151,935	140,875	[1]
Amortized cost, Total	531,795	497,385
Gross unrealized gains, Total	1,650	1,398
Gross unrealized losses, Total	5,581	7,868
Estimated fair value, Total	527,864	490,915
Obligations of U.S. government sponsored enterprises [Member]
Available-for-sale Securities [Abstract]
Amortized cost	2,011	2,028
Gross unrealized gains	8	16
Gross unrealized losses	0	0
Total	2,019	2,044
Residential mortgage-backed securities - GSE [Member]
Available-for-sale Securities [Abstract]
Amortized cost	291,955	295,300
Gross unrealized gains	631	438
Gross unrealized losses	4,445	5,593
Total	288,141	290,145
Held-to-maturity Securities [Abstract]
Amortized cost	123,735	132,396
Gross unrealized gains	210	116
Gross unrealized losses	763	1,635
Total	123,182	130,877
Residential mortgage-backed securities - Private [Member]
Available-for-sale Securities [Abstract]
Amortized cost	14,456	16,455
Gross unrealized gains	631	820
Gross unrealized losses	4	4
Total	15,083	17,271
Held-to-maturity Securities [Abstract]
Amortized cost	18,875
Gross unrealized gains	0
Gross unrealized losses	255
Total	18,620
Commercial mortgage-backed securities - GSE [Member]
Available-for-sale Securities [Abstract]
Amortized cost	22,080	22,377
Gross unrealized gains	68	0
Gross unrealized losses	0	419
Total	22,148	21,958
Commercial mortgage-backed securities - Private [Member]
Available-for-sale Securities [Abstract]
Amortized cost	17,879	10,365
Gross unrealized gains	20	0
Gross unrealized losses	86	150
Total	17,813	10,215
Held-to-maturity Securities [Abstract]
Amortized cost	10,060	10,065
Gross unrealized gains	73	0
Gross unrealized losses	0	67
Total	10,133	9,998
Corporate notes [Member]
Available-for-sale Securities [Abstract]
Amortized cost	30,744	8,399
Gross unrealized gains	9	8
Gross unrealized losses	28	0
Total	$ 30,725	$ 8,407

[1] Derived from audited consolidated financial statements