Investment Securities (Continuous Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013 securities	Dec. 31, 2012
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	$ 353,468	$ 134,237
Less than 12 months, gross unrealized losses	20,974	1,375
12 months or more, estimated fair value	643	7,027
12 months or more, gross unrealized losses	10	44
Total, estimated fair value	354,111	141,264
Total, gross unrealized losses	20,984	1,419
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	129,140
Less than 12 months, gross unrealized losses	6,052
12 months or more, estimated fair value	0
12 months or more, gross unrealized losses	0
Total, estimated fair value	129,140
Total, gross unrealized losses	6,052
Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	482,608
Less than 12 months, gross unrealized losses	27,026
12 months or more, estimated fair value	643
12 months or more, gross unrealized losses	10
Total, estimated fair value	483,251
Total, gross unrealized losses	27,036
12 months or more, number of securities	1
Residential mortgage-backed securities - GSE [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	322,395	123,489
Less than 12 months, gross unrealized losses	18,658	904
12 months or more, estimated fair value	0	7,027
12 months or more, gross unrealized losses	0	44
Total, estimated fair value	322,395	130,516
Total, gross unrealized losses	18,658	948
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	119,794
Less than 12 months, gross unrealized losses	5,324
12 months or more, estimated fair value	0
12 months or more, gross unrealized losses	0
Total, estimated fair value	119,794
Total, gross unrealized losses	5,324
Residential mortgage-backed securities - Private [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	0	7,499
Less than 12 months, gross unrealized losses	0	454
12 months or more, estimated fair value	643	0
12 months or more, gross unrealized losses	10	0
Total, estimated fair value	643	7,499
Total, gross unrealized losses	10	454
Commercial mortgage-backed securities - Private [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	21,498
Less than 12 months, gross unrealized losses	1,461
12 months or more, estimated fair value	0
12 months or more, gross unrealized losses	0
Total, estimated fair value	21,498
Total, gross unrealized losses	1,461
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	9,346
Less than 12 months, gross unrealized losses	728
12 months or more, estimated fair value	0
12 months or more, gross unrealized losses	0
Total, estimated fair value	9,346
Total, gross unrealized losses	728
Corporate notes [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	9,575	3,249
Less than 12 months, gross unrealized losses	855	17
12 months or more, estimated fair value	0	0
12 months or more, gross unrealized losses	0	0
Total, estimated fair value	9,575	3,249
Total, gross unrealized losses	$ 855	$ 17