Investment Securities (Continuous Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	$ 20,593	$ 233,973
Less than 12 months, gross unrealized losses	186	3,567
12 months or more, estimated fair value	200,225	132,784
12 months or more, gross unrealized losses	2,404	5,734
Total, estimated fair value	220,818	366,757
Total, gross unrealized losses	2,590	9,301
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	16,845	110,312
Less than 12 months, gross unrealized losses	32	1,953
12 months or more, estimated fair value	13,628	34,872
12 months or more, gross unrealized losses	109	829
Total, estimated fair value	30,473	145,184
Total, gross unrealized losses	141	2,782
Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	37,438	344,285
Less than 12 months, gross unrealized losses	218	5,520
12 months or more, estimated fair value	213,853	167,656
12 months or more, gross unrealized losses	2,513	6,563
Total, estimated fair value	251,291	511,941
Total, gross unrealized losses	2,731	12,083
Residential mortgage-backed securities - GSE [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	137,998
Less than 12 months, gross unrealized losses	0	2,560
12 months or more, estimated fair value	189,610	132,148
12 months or more, gross unrealized losses	2,379	5,729
Total, estimated fair value	189,610	270,146
Total, gross unrealized losses	2,379	8,289
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	83,014
Less than 12 months, gross unrealized losses	0	1,481
12 months or more, estimated fair value	13,628	34,872
12 months or more, gross unrealized losses	109	829
Total, estimated fair value	13,628	117,886
Total, gross unrealized losses	109	2,310
Residential mortgage-backed securities - Private [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	2,970	26,265
Less than 12 months, gross unrealized losses	32	231
12 months or more, estimated fair value	621	636
12 months or more, gross unrealized losses	12	5
Total, estimated fair value	3,591	26,901
Total, gross unrealized losses	44	236
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	16,845	17,414
Less than 12 months, gross unrealized losses	32	298
12 months or more, estimated fair value	0	0
12 months or more, gross unrealized losses	0	0
Total, estimated fair value	16,845	17,414
Total, gross unrealized losses	32	298
Commercial mortgage-backed securities - GSE [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	21,612
Less than 12 months, gross unrealized losses	0	368
12 months or more, estimated fair value	0	0
12 months or more, gross unrealized losses	0	0
Total, estimated fair value	0	21,612
Total, gross unrealized losses	0	368
Commercial mortgage-backed securities - Private [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	7,399	17,575
Less than 12 months, gross unrealized losses	150	294
12 months or more, estimated fair value	0	0
12 months or more, gross unrealized losses	0	0
Total, estimated fair value	7,399	17,575
Total, gross unrealized losses	150	294
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value		9,884
Less than 12 months, gross unrealized losses		174
12 months or more, estimated fair value		0
12 months or more, gross unrealized losses		0
Total, estimated fair value		9,884
Total, gross unrealized losses		174
Corporate notes [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	10,224	30,523
Less than 12 months, gross unrealized losses	4	114
12 months or more, estimated fair value	9,994	0
12 months or more, gross unrealized losses	13	0
Total, estimated fair value	20,218	30,523
Total, gross unrealized losses	$ 17	$ 114