Investment Securities (Continuous Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	$ 124,493	$ 1,154
Less than 12 months, gross unrealized losses	994	4
12 months or more, estimated fair value	138,683	277,630
12 months or more, gross unrealized losses	3,569	6,162
Total, estimated fair value	263,176	278,784
Total, gross unrealized losses	4,563	6,166
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	64,333	0
Less than 12 months, gross unrealized losses	714	0
12 months or more, estimated fair value	36,624	122,876
12 months or more, gross unrealized losses	304	1,702
Total, estimated fair value	100,957	122,876
Total, gross unrealized losses	1,018	1,702
Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	188,826	1,154
Less than 12 months, gross unrealized losses	1,708	4
12 months or more, estimated fair value	175,307	400,506
12 months or more, gross unrealized losses	3,873	7,864
Total, estimated fair value	364,133	401,660
Total, gross unrealized losses	5,581	7,868
Residential mortgage-backed securities - GSE [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	91,601	0
Less than 12 months, gross unrealized losses	880	0
12 months or more, estimated fair value	137,652	245,457
12 months or more, gross unrealized losses	3,565	5,593
Total, estimated fair value	229,253	245,457
Total, gross unrealized losses	4,445	5,593
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	45,712	0
Less than 12 months, gross unrealized losses	459	0
12 months or more, estimated fair value	36,624	112,878
12 months or more, gross unrealized losses	304	1,635
Total, estimated fair value	82,336	112,878
Total, gross unrealized losses	763	1,635
Residential mortgage-backed securities - Private [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	1,154
Less than 12 months, gross unrealized losses	0	4
12 months or more, estimated fair value	1,031	0
12 months or more, gross unrealized losses	4	0
Total, estimated fair value	1,031	1,154
Total, gross unrealized losses	4	4
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	18,621
Less than 12 months, gross unrealized losses	255
12 months or more, estimated fair value	0
12 months or more, gross unrealized losses	0
Total, estimated fair value	18,621
Total, gross unrealized losses	255
Commercial mortgage-backed securities - GSE [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	0
Less than 12 months, gross unrealized losses	0	0
12 months or more, estimated fair value	0	21,958
12 months or more, gross unrealized losses	0	419
Total, estimated fair value	0	21,958
Total, gross unrealized losses	0	419
Commercial mortgage-backed securities - Private [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	12,564	0
Less than 12 months, gross unrealized losses	86	0
12 months or more, estimated fair value	0	10,215
12 months or more, gross unrealized losses	0	150
Total, estimated fair value	12,564	10,215
Total, gross unrealized losses	86	150
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	0
Less than 12 months, gross unrealized losses	0	0
12 months or more, estimated fair value	0	9,998
12 months or more, gross unrealized losses	0	67
Total, estimated fair value	0	9,998
Total, gross unrealized losses	0	$ 67
Corporate notes [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	20,328
Less than 12 months, gross unrealized losses	28
Total, estimated fair value	20,328
Total, gross unrealized losses	$ 28