Investment Securities (Gross Unrealized Loss Table) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013 securities	Dec. 31, 2012 securities	Mar. 31, 2012 securities
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 493,473	$ 213,685	$ 181,287
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(4,813)	(1,031)	(1,902)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	86	41	64
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	51,225	50,056	46,659
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(10,330)	(11,891)	(14,843)
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	8	11	9
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	544,698	263,741	227,946
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(15,143)	(12,922)	(16,745)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	70,715	23,956
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(583)	(86)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	58	13
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	70,715	23,956
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	(583)	(86)
U.S. States and political subdivisions [Member]
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	33,648	14,110	26,915
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(790)	(229)	(751)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	51	24	39
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0	0
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	0	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	33,648	14,110	26,915
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(790)	(229)	(751)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	29,823	6,543
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(244)	(70)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	54	12
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	29,823	6,543
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	(244)	(70)
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	45,345	14	40,036
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(663)	0	(213)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	5	1	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	13	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0	0
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	0	1	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	45,345	27	40,036
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(663)	0	(213)
Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	30,799	31,237	12,329
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(659)	(406)	(60)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	3	3	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0	0
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	0	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	30,799	31,237	12,329
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(659)	(406)	(60)
Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises [Member]
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	339,462	133,008	4,322
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(2,354)	(258)	(2)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	21	9	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	389	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	(2)	0
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	0	1	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	339,462	133,397	4,322
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(2,354)	(260)	(2)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value		17,413
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		(16)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions		1
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		0
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value		17,413
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses		(16)
Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency [Member]
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		0	0
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions		0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		2	2
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		0	0
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions		1	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		2	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		0	0
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	44,219	35,316	64,435
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(347)	(138)	(534)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	6	4	6
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0	0
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	0	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	44,219	35,316	64,435
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(347)	(138)	(534)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	40,892
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(339)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	4
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	40,892
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	(339)
Corporate debt securities [Member]
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0	33,250
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0	0	(342)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	0	0	12
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	51,225	49,652	46,657
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(10,330)	(11,889)	(14,843)
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	8	8	8
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	51,225	49,652	79,907
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$ (10,330)	$ (11,889)	$ (15,185)