Securities (Details 1) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Available-for-sale
Total available-for-sale securities one year or less	$ 11,270
Total available-for-sale securities one to five years	93,515
Total available-for-sale securities five to ten years	100,785
Total available-for-sale securities after ten years	96,251
Total available for sale securities mortgage backed and equity	721,303
Available-for-sale, at fair value	1,023,124	1,016,340
Held-to-maturity
Total held-to-maturity securities, one year or less, fair value	1,177
Total held-to-maturity securities one to five years	7,840
Total held-to-maturity securities five to ten years	57,128
Total held-to-maturity securities after ten years	334,169
Held to maturity mortgage backed and equity	206,718
Held-to-maturity, Estimated Fair Value	607,032	621,472
Total securities one year or less	12,447
Total securities one to five years	101,355
Total securities five to ten years fair value	157,913
Total securities after ten years fair value	430,420
Total securities mortgage- backed and equity	928,021
Total securities fair value	1,630,156
Other Government Agencies [Member]
Available-for-sale
Total available-for-sale securities one year or less	2,571
Total available-for-sale securities one to five years	15,104
Total available-for-sale securities five to ten years	40,790
Total available-for-sale securities after ten years	37,605
Total available for sale securities mortgage backed and equity
Available-for-sale, at fair value	96,070	198,720
Residential mortgage-backed securities and collateralized mortgage obligations of government agencies [Member]
Available-for-sale
Total available-for-sale securities one year or less
Total available-for-sale securities one to five years
Total available-for-sale securities five to ten years
Total available-for-sale securities after ten years
Total available for sale securities mortgage backed and equity	715,726
Available-for-sale, at fair value	715,726	588,092
Held-to-maturity
Total held-to-maturity securities, one year or less, fair value
Total held-to-maturity securities one to five years
Total held-to-maturity securities five to ten years
Total held-to-maturity securities after ten years
Held to maturity mortgage backed and equity	206,256
Held-to-maturity, Estimated Fair Value	206,256	255,074
Other residential collateralized mortgage obligations [Member]
Held-to-maturity
Total held-to-maturity securities, one year or less, fair value
Total held-to-maturity securities one to five years
Total held-to-maturity securities five to ten years
Total held-to-maturity securities after ten years
Held to maturity mortgage backed and equity	462
Held-to-maturity, Estimated Fair Value	462	791
Obligations of States and Political Subdivisions [Member]
Available-for-sale
Total available-for-sale securities one year or less	5,446
Total available-for-sale securities one to five years	47,937
Total available-for-sale securities five to ten years	58,109
Total available-for-sale securities after ten years	55,689
Total available for sale securities mortgage backed and equity
Available-for-sale, at fair value	167,181	180,433
Held-to-maturity
Total held-to-maturity securities, one year or less, fair value	1,177
Total held-to-maturity securities one to five years	7,840
Total held-to-maturity securities five to ten years	57,128
Total held-to-maturity securities after ten years	334,169
Held to maturity mortgage backed and equity
Held-to-maturity, Estimated Fair Value	400,314	364,073
Corporate Debt Securities [Member]
Available-for-sale
Total available-for-sale securities one year or less	3,253
Total available-for-sale securities one to five years	30,474
Total available-for-sale securities five to ten years	1,886
Total available-for-sale securities after ten years	2,957
Total available for sale securities mortgage backed and equity
Available-for-sale, at fair value	38,570	44,066
Held-to-maturity
Held-to-maturity, Estimated Fair Value		1,534
Equity Securities [Member]
Available-for-sale
Total available-for-sale securities one year or less
Total available-for-sale securities one to five years
Total available-for-sale securities five to ten years
Total available-for-sale securities after ten years
Total available for sale securities mortgage backed and equity	5,577
Available-for-sale, at fair value	$ 5,577	$ 5,029