Investment Securities (Continuous Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013 securities	Dec. 31, 2012
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	$ 310,157	$ 129,971
Less than 12 months, gross unrealized losses	4,154	1,342
12 months or more, estimated fair value	7,259	11,293
12 months or more, gross unrealized losses	73	77
Total, estimated fair value	317,416	141,264
Total, gross unrealized losses	4,227	1,419
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
12 months or more, number of securities	0
Residential mortgage-backed securities - GSE [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	284,396	123,489
Less than 12 months, gross unrealized losses	3,279	904
12 months or more, estimated fair value	0	7,027
12 months or more, gross unrealized losses	0	44
Total, estimated fair value	284,396	130,516
Total, gross unrealized losses	3,279	948
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	48,036
Less than 12 months, gross unrealized losses	272
12 months or more, estimated fair value	0
12 months or more, gross unrealized losses	0
Total, estimated fair value	48,036
Total, gross unrealized losses	272
Residential mortgage-backed securities - private [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	3,365	6,482
Less than 12 months, gross unrealized losses	217	438
12 months or more, estimated fair value	4,025	1,017
12 months or more, gross unrealized losses	33	16
Total, estimated fair value	7,390	7,499
Total, gross unrealized losses	250	454
Commercial mortgage-backed securities - private [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 months, estimated fair value	22,396
Less than 12 months, gross unrealized losses	658
12 months or more, estimated fair value	0
12 months or more, gross unrealized losses	0
Total, estimated fair value	22,396
Total, gross unrealized losses	658
Corporate notes [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	3,234	3,249
12 months or more, gross unrealized losses	40	17
Total, estimated fair value	3,234	3,249
Total, gross unrealized losses	$ 40	$ 17