Investment Securities (Continuous Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014 securities	Dec. 31, 2013 securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	$ 14	$ 232,060
Less than 12 months, gross unrealized losses	0	17,408
12 months or more, estimated fair value	332,532	97,940
12 months or more, gross unrealized losses	13,061	9,083
Total, estimated fair value	332,546	330,000
Total, gross unrealized losses	13,061	26,491
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	141,125
Less than 12 months, gross unrealized losses	0	10,670
12 months or more, estimated fair value	142,288	0
12 months or more, gross unrealized losses	4,767	0
Total, estimated fair value	142,288	141,125
Total, gross unrealized losses	4,767	10,670
Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	14	373,185
Less than 12 months, gross unrealized losses	0	28,078
12 months or more, estimated fair value	474,820	97,940
12 months or more, gross unrealized losses	17,828	9,083
Total, estimated fair value	474,834	471,125
Total, gross unrealized losses	17,828	37,161
12 months or more, number of securities	49	10
Residential mortgage-backed securities - GSE [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	14	222,475
Less than 12 months, gross unrealized losses	0	16,585
12 months or more, estimated fair value	300,334	76,501
12 months or more, gross unrealized losses	12,298	7,755
Total, estimated fair value	300,348	298,976
Total, gross unrealized losses	12,298	24,340
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	131,817
Less than 12 months, gross unrealized losses	0	9,907
12 months or more, estimated fair value	132,398	0
12 months or more, gross unrealized losses	4,589	0
Total, estimated fair value	132,398	131,817
Total, gross unrealized losses	4,589	9,907
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	22,052	21,439
12 months or more, gross unrealized losses	522	1,328
Total, estimated fair value	22,052	21,439
Total, gross unrealized losses	522	1,328
Commercial mortgage-backed securities - Private [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	9,585
Less than 12 months, gross unrealized losses	0	823
12 months or more, estimated fair value	10,146	0
12 months or more, gross unrealized losses	241	0
Total, estimated fair value	10,146	9,585
Total, gross unrealized losses	241	823
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	9,308
Less than 12 months, gross unrealized losses	0	763
12 months or more, estimated fair value	9,890	0
12 months or more, gross unrealized losses	178	0
Total, estimated fair value	9,890	9,308
Total, gross unrealized losses	$ 178	$ 763