Securities (Amortized cost and fair value of debt securities by contractrual maturity) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Available-for-sale Securities
Securities available for sale, amortized cost	$ 628,527	$ 664,139
Available-for-sale securities, fair value	612,151	675,109
Held-to-maturity Securities
Securities held to maturity, amortized cost	277,224	269,783
Securities held to maturity, fair value	262,976	273,671
Debt Securities [Member]
Held-to-maturity Securities
Due in one year or less, amortized cost	0
Due after one year through five years, amortized cost	5,000
Due after five years through ten years, amortized cost	70,000
Due after ten years, amortized cost	82,070
Securities held to maturity, amortized cost	157,070
Due in one year or less, fair value	0
Due after one year through five years, fair value	5,094
Due after five years through ten years, fair value	63,648
Due after ten years, amortized cost	75,166
Securities held to maturity, fair value	143,908
Residential mortgage-backed securities [Member]
Held-to-maturity Securities
Securities held to maturity, amortized cost	16,793	23,827
Securities held to maturity, fair value	17,848	25,716
Agency CMOs [Member]
Held-to-maturity Securities
Securities held to maturity, amortized cost	103,361	49,051
Securities held to maturity, fair value	101,220	50,638
Debt Securities [Member]
Available-for-sale Securities
Due in one year or less, amortized cost	0
Due after one year through five years, amortized cost	0
Due after five years through ten years, amortized cost	47,482
Due after ten years, amortized cost	13,410
Securities available for sale, amortized cost	60,892
Due in one year or less, fair value	0
Due after one year through five years, fair value	0
Due after five years through ten years, fair value	43,453
Due after ten years, fair value	12,605
Available-for-sale securities, fair value	56,058
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Securities available for sale, amortized cost	67,323	55,614
Available-for-sale securities, fair value	65,061	57,210
Agency CMOs [Member]
Available-for-sale Securities
Securities available for sale, amortized cost	500,312	547,641
Available-for-sale securities, fair value	$ 491,032	$ 556,867