Investment Securities (Continuous Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014 securities	Dec. 31, 2013 securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	$ 0	$ 232,060
Less than 12 months, gross unrealized losses	0	17,408
12 months or more, estimated fair value	312,911	97,940
12 months or more, gross unrealized losses	12,816	9,083
Total, estimated fair value	312,911	330,000
Total, gross unrealized losses	12,816	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	139,582	0
12 months or more, gross unrealized losses	5,102	0
Total, estimated fair value	139,582	141,125
Total, gross unrealized losses	5,102	10,670
Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	373,185
Less than 12 months, gross unrealized losses	0	28,078
12 months or more, estimated fair value	452,493	97,940
12 months or more, gross unrealized losses	17,918	9,083
Total, estimated fair value	452,493	471,125
Total, gross unrealized losses	17,918	37,161
12 months or more, number of securities	36	10
Residential mortgage-backed securities - GSE [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	222,475
Less than 12 months, gross unrealized losses	0	16,585
12 months or more, estimated fair value	281,209	76,501
12 months or more, gross unrealized losses	11,666	7,755
Total, estimated fair value	281,209	298,976
Total, gross unrealized losses	11,666	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	129,759	0
12 months or more, gross unrealized losses	4,859	0
Total, estimated fair value	129,759	131,817
Total, gross unrealized losses	4,859	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	21,645	21,439
12 months or more, gross unrealized losses	831	1,328
Total, estimated fair value	21,645	21,439
Total, gross unrealized losses	831	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	10,057	0
12 months or more, gross unrealized losses	319	0
Total, estimated fair value	10,057	9,585
Total, gross unrealized losses	319	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	9,823	0
12 months or more, gross unrealized losses	243	0
Total, estimated fair value	9,823	9,308
Total, gross unrealized losses	$ 243	$ 763