Securities (Amortized cost and fair value of debt securities by contractrual maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale Securities
Securities available for sale, amortized cost	$ 404,026	$ 533,999
Available-for-sale securities, fair value	401,610	528,038
Held-to-maturity Securities
Securities held to maturity, amortized cost	325,378	324,994
Securities held to maturity, fair value	326,410	319,923
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	8,145
Due after five years through ten years, amortized cost	50,425
Due after ten years, amortized cost	5,420
Securities available for sale, amortized cost	63,990
Due in one year or less, fair value	0
Due after one year through five years, fair value	8,203
Due after five years through ten years, fair value	50,289
Due after ten years, fair value	5,334
Available-for-sale securities, fair value	63,826
Held-to-maturity 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	111,382
Due after ten years, amortized cost	37,457
Securities held to maturity, amortized cost	148,839
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	110,107
Due after ten years, fair value	37,796
Securities held to maturity, fair value	147,903
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Securities available for sale, amortized cost	54,963	60,196
Available-for-sale securities, fair value	55,123	60,149
Held-to-maturity Securities
Securities held to maturity, amortized cost	11,674	14,226
Securities held to maturity, fair value	11,940	14,706
Agency CMOs [Member]
Available-for-sale Securities
Securities available for sale, amortized cost	285,073	409,823
Available-for-sale securities, fair value	282,661	405,009
Held-to-maturity Securities
Securities held to maturity, amortized cost	164,865	146,952
Securities held to maturity, fair value	$ 166,567	$ 145,890