Investments (Aggregate Values and Unrealized Gains and Losses) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investment securities available for sale
Cost	$ 5,632,720	$ 5,404,335
Gross Unrealized Gains	38,685	28,188
Gross Unrealized Losses	23,311	44,820
Fair Value	5,648,094	5,387,703
Investment securities held to maturity
Cost	607	907
U. S. Treasury
Investment securities available for sale
Cost	1,888,647	373,223
Gross Unrealized Gains	583	259
Gross Unrealized Losses	1,420	45
Fair Value	1,887,810	373,437
Government Agency
Investment securities available for sale
Cost	1,128,752	2,543,223
Gross Unrealized Gains	1,294	1,798
Gross Unrealized Losses	393	792
Fair Value	1,129,653	2,544,229
Mortgage Backed Securities, Other [Member]
Investment securities available for sale
Cost	2,591,641	2,486,297
Gross Unrealized Gains	7,322	4,526
Gross Unrealized Losses	21,498	43,950
Fair Value	2,577,465	2,446,873
Investment securities held to maturity
Cost	607	907
Held To Maturity Securities Accumulated Unrecognized Holding Gain	31	67
Held To Maturity Securities Accumulated Unrecognized Holding Loss	0	0
Fair Value	638	974
Equity Securities
Investment securities available for sale
Cost	543	543
Gross Unrealized Gains	29,485	21,604
Gross Unrealized Losses	0	0
Fair Value	30,028	22,147
Equity Securities \| Bancorporation
Investment securities available for sale
Fair Value	29,600
State, County and Municipal
Investment securities available for sale
Cost	125	186
Gross Unrealized Gains	1	1
Gross Unrealized Losses	0	0
Fair Value	126	187
Other Debt Obligations
Investment securities available for sale
Cost	23,012	863
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	33
Fair Value	$ 23,012	$ 830

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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