Investment Securities (Gross Unrealized Loss Table) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 245,893	$ 424,916	$ 1,753,704
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(1,647)	(2,807)	(44,907)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	46	53	187
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,172,260	1,485,458	380,281
available for sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss at end of period	(29,123)	(49,824)	(27,186)
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	114	162	63.000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,418,153	1,910,374	2,133,985
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss at End of Period	(30,770)	(52,631)	(72,093)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	90,604	125,775	1,974,519
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(1,287)	(277)	(61,484)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	30	30	842
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,389,498	1,577,797	612,989
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(30,046)	(49,520)	(31,058)
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	83	108	44
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	1,480,102	1,703,572	2,587,508
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	(31,333)	(49,797)	(92,542)
US Government Agencies Debt Securities
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	0	0	23,883
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0	0	(1,117)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	0	0	1
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	24,822	24,463	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(178)	(537)	0
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	1	1	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	24,822	24,463	23,883
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	(178)	(537)	(1,117)
U.S. States and political subdivisions debt securities
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	14,380	5,637	32,307
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(117)	(11)	(937)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	23	11	53
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	6,004	22,528	17,231
available for sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss at end of period	(269)	(455)	(1,158)
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	10	36	29
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	20,384	28,165	49,538
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss at End of Period	(386)	(466)	(2,095)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	38,202	9,085	476,766
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(1,093)	(17)	(6,833)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	26	9	735
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,448	18,371	15,544
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(54)	(174)	(353)
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	6	21	14
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	42,650	27,456	492,310
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	(1,147)	(191)	(7,186)
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	74,517	50,126	399,152
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(360)	(182)	(9,543)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	5	5	28
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	108,052	199,773	15,013
available for sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss at end of period	(1,589)	(3,036)	(963)
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	8	14	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	182,569	249,899	414,165
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss at End of Period	(1,949)	(3,218)	(10,506)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	28,386	0	295,148
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(123)	0	(7,471)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	2	0	16
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	110,329	185,361	19,730
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(1,554)	(3,045)	(1,113)
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	6	10	1
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	138,715	185,361	314,878
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	(1,677)	(3,045)	(8,584)
Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	49,129	12,284	63,129
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(175)	(55)	(1,206)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	7	2	8
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	17,690	45,485	16,891
available for sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss at end of period	(486)	(1,316)	(955)
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	2	6	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	66,819	57,769	80,020
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss at End of Period	(661)	(1,371)	(2,161)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	0	9,950	50,533
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0	(4)	(877)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	0	2	8
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	9,554	16,735	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(108)	(325)	0
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	1	2	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	9,554	26,685	50,533
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	(108)	(329)	(877)
Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	70,574	243,970	966,458
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(762)	(906)	(28,054)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	6	15	62
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	745,621	905,478	273,543
available for sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss at end of period	(13,095)	(25,319)	(13,750)
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	53	64	18
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	816,195	1,149,448	1,240,001
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss at End of Period	(13,857)	(26,225)	(41,804)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	19,016	28,333	865,651
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(71)	(149)	(36,384)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	1	3	42
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,095,375	1,161,297	558,256
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(24,775)	(38,726)	(28,350)
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	56	58	27
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	1,114,391	1,189,630	1,423,907
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	(24,846)	(38,875)	(64,734)
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	13,206	31,375	90,804
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(24)	(229)	(1,475)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	2	4	8
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	61,132	67,169	6,014
available for sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss at end of period	(358)	(1,176)	(338)
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	6	7	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	74,338	98,544	96,818
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss at End of Period	(382)	(1,405)	(1,813)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	0	41,474	200,487
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0	(55)	(8,507)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	0	3	18
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	144,970	171,570	19,459
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(3,377)	(6,713)	(1,242)
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	13	16	2
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	144,970	213,044	219,946
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	(3,377)	(6,768)	(9,749)
Collateralized Loan Obligations
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	24,087	79,042	201,854
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(209)	(1,406)	(3,692)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	3	15	28
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	181,498	193,687	0
available for sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss at end of period	(3,922)	(8,207)	0
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	27	27	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	205,585	272,729	201,854
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss at End of Period	(4,131)	(9,613)	(3,692)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	0
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	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	0
Corporate debt securities
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0	0	0
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	0	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	52,263	51,338	51,588
available for sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss at end of period	(9,404)	(10,315)	(10,022)
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	52,263	51,338	51,588
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss at End of Period	(9,404)	(10,315)	(10,022)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	0	36,933	62,051
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0	(52)	(295)
Held to Maturity Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	0	13	22
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0	0
Held to Maturity Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	0	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	0	36,933	62,051
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	0	(52)	(295)
US Treasury Securities
Securities available for sale
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	2,482
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0	(18)
Available for Sale Securities in Unrealized Loss Positions Less than Twelve Months Qualitative Disclosure Number of Positions	0	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
available for sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss at end of period	0	0
Available for Sale Securities in Unrealized Loss Positions Twelve Months or Longer Qualitative Disclosure Number of Positions	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	0	2,482
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss at End of Period	0	(18)
Securities held to maturity
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	5,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0
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	5,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses	$ 0