Investment Securities (Continuous Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	$ 197,991	$ 1,154
Less than 12 months, gross unrealized losses	3,526	4
12 months or more, estimated fair value	137,765	277,630
12 months or more, gross unrealized losses	6,482	6,162
Total, estimated fair value	335,756	278,784
Total, gross unrealized losses	10,008	6,166
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	116,335	0
Less than 12 months, gross unrealized losses	2,154	0
12 months or more, estimated fair value	37,255	122,876
12 months or more, gross unrealized losses	905	1,702
Total, estimated fair value	153,590	122,876
Total, gross unrealized losses	3,059	1,702
Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	314,326	1,154
Less than 12 months, gross unrealized losses	5,680	4
12 months or more, estimated fair value	175,020	400,506
12 months or more, gross unrealized losses	7,387	7,864
Total, estimated fair value	489,346	401,660
Total, gross unrealized losses	13,067	7,868
Residential mortgage-backed securities - GSE [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	124,950	0
Less than 12 months, gross unrealized losses	2,900	0
12 months or more, estimated fair value	137,765	245,457
12 months or more, gross unrealized losses	6,482	5,593
Total, estimated fair value	262,715	245,457
Total, gross unrealized losses	9,382	5,593
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	86,937	0
Less than 12 months, gross unrealized losses	1,880	0
12 months or more, estimated fair value	37,255	112,878
12 months or more, gross unrealized losses	905	1,635
Total, estimated fair value	124,192	112,878
Total, gross unrealized losses	2,785	1,635
Residential mortgage-backed securities - Private [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	1,105	1,154
Less than 12 months, gross unrealized losses	4	4
12 months or more, estimated fair value	0	0
12 months or more, gross unrealized losses	0	0
Total, estimated fair value	1,105	1,154
Total, gross unrealized losses	4	4
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	19,524
Less than 12 months, gross unrealized losses	85
12 months or more, estimated fair value	0
12 months or more, gross unrealized losses	0
Total, estimated fair value	19,524
Total, gross unrealized losses	85
Commercial mortgage-backed securities - GSE [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	21,872	0
Less than 12 months, gross unrealized losses	308	0
12 months or more, estimated fair value	0	21,958
12 months or more, gross unrealized losses	0	419
Total, estimated fair value	21,872	21,958
Total, gross unrealized losses	308	419
Commercial mortgage-backed securities - Private [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	19,236	0
Less than 12 months, gross unrealized losses	261	0
12 months or more, estimated fair value	0	10,215
12 months or more, gross unrealized losses	0	150
Total, estimated fair value	19,236	10,215
Total, gross unrealized losses	261	150
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	9,874	0
Less than 12 months, gross unrealized losses	189	0
12 months or more, estimated fair value	0	9,998
12 months or more, gross unrealized losses	0	67
Total, estimated fair value	9,874	9,998
Total, gross unrealized losses	189	$ 67
Corporate notes [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	30,828
Less than 12 months, gross unrealized losses	53
Total, estimated fair value	30,828
Total, gross unrealized losses	$ 53