Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Available-for-sale Securities [Abstract]
Amortized cost	$ 390,324	$ 354,924	[1]
Gross unrealized gains	1,051	1,282
Gross unrealized losses	10,008	6,166
Estimated fair value	381,367	350,040	[1]
Held-to-maturity Securities [Abstract]
Amortized cost	156,648	142,461
Gross unrealized gains	0	116
Gross unrealized losses	3,059	1,702
Estimated fair value	153,589	140,875	[1]
Amortized cost, Total	546,972	497,385
Gross unrealized gains, Total	1,051	1,398
Gross unrealized losses, Total	13,067	7,868
Estimated fair value, Total	534,956	490,915
Obligations of U.S. government sponsored enterprises [Member]
Available-for-sale Securities [Abstract]
Amortized cost	2,016	2,028
Gross unrealized gains	12	16
Gross unrealized losses	0	0
Estimated fair value	2,028	2,044
Residential mortgage-backed securities - GSE [Member]
Available-for-sale Securities [Abstract]
Amortized cost	300,522	295,300
Gross unrealized gains	355	438
Gross unrealized losses	9,382	5,593
Estimated fair value	291,495	290,145
Held-to-maturity Securities [Abstract]
Amortized cost	126,977	132,396
Gross unrealized gains	0	116
Gross unrealized losses	2,785	1,635
Estimated fair value	124,192	130,877
Residential mortgage-backed securities - Private [Member]
Available-for-sale Securities [Abstract]
Amortized cost	15,228	16,455
Gross unrealized gains	684	820
Gross unrealized losses	4	4
Estimated fair value	15,908	17,271
Held-to-maturity Securities [Abstract]
Amortized cost	19,609
Gross unrealized gains	0
Gross unrealized losses	85
Estimated fair value	19,524
Commercial mortgage-backed securities - GSE [Member]
Available-for-sale Securities [Abstract]
Amortized cost	22,180	22,377
Gross unrealized gains	0	0
Gross unrealized losses	308	419
Estimated fair value	21,872	21,958
Commercial mortgage-backed securities - Private [Member]
Available-for-sale Securities [Abstract]
Amortized cost	19,497	10,365
Gross unrealized gains	0	0
Gross unrealized losses	261	150
Estimated fair value	19,236	10,215
Held-to-maturity Securities [Abstract]
Amortized cost	10,062	10,065
Gross unrealized gains	0	0
Gross unrealized losses	189	67
Estimated fair value	9,873	9,998
Corporate notes [Member]
Available-for-sale Securities [Abstract]
Amortized cost	30,881	8,399
Gross unrealized gains	0	8
Gross unrealized losses	53	0
Estimated fair value	$ 30,828	$ 8,407

[1] Derived from audited consolidated financial statements