Investment Securities Schedule of Amortized Cost and Fair Values of Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Statement of Investments [Line Items]
Held-to-maturity Securities	$ 206	$ 292
Held-to-maturity Securities, Unrecognized Holding Gain	18	27
Held-to-maturity Securities, Unrecognized Holding Loss	0	0
Held-to-maturity Securities, Fair Value	224	319
Available-for-sale Securities, Amortized Cost Basis	2,718,217	2,752,220
Available-for-sale Securities, Gross Unrealized Gains	45,889	74,497
Available-for-sale Securities, Gross Unrealized Losses	(77,663)	(32,992)
Available-for-sale Securities	2,686,443	2,793,725
Equity Securities [Member]
Statement of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis	123,111	118,465
Available-for-sale Securities, Gross Unrealized Gains	8,596	5,016
Available-for-sale Securities, Gross Unrealized Losses	(130)	(918)
Available-for-sale Securities	131,577	122,563
U.S. Government Securities [Member]
Statement of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis	2,250	325
Available-for-sale Securities, Gross Unrealized Gains	0	0
Available-for-sale Securities, Gross Unrealized Losses	0	0
Available-for-sale Securities	2,250	325
U.S. Government-Sponsored Agency Securities [Member]
Statement of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis	828	2,376
Available-for-sale Securities, Gross Unrealized Gains	8	21
Available-for-sale Securities, Gross Unrealized Losses	(1)	0
Available-for-sale Securities	835	2,397
State and Municipal Securities [Member]
Statement of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis	288,659	301,842
Available-for-sale Securities, Gross Unrealized Gains	7,552	13,763
Available-for-sale Securities, Gross Unrealized Losses	(2,698)	(86)
Available-for-sale Securities	293,513	315,519
Corporate Debt Securities [Member]
Statement of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis	108,272	112,162
Available-for-sale Securities, Gross Unrealized Gains	5,115	7,858
Available-for-sale Securities, Gross Unrealized Losses	(6,836)	(7,178)
Available-for-sale Securities	106,551	112,842
Collateralized Mortgage Obligations [Member]
Statement of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,113,753	1,195,234
Available-for-sale Securities, Gross Unrealized Gains	9,373	16,008
Available-for-sale Securities, Gross Unrealized Losses	(40,149)	(123)
Available-for-sale Securities	1,082,977	1,211,119
Mortgage Backed Securities, Other [Member]
Statement of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis	909,292
Available-for-sale Securities, Gross Unrealized Gains	15,209
Available-for-sale Securities, Gross Unrealized Losses	(10,271)
Available-for-sale Securities	914,230
Mortgage-Backed Securities [Member]
Statement of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis		847,790
Available-for-sale Securities, Gross Unrealized Gains		31,831
Available-for-sale Securities, Gross Unrealized Losses		0
Available-for-sale Securities		879,621
Auction Rate Securities [Member]
Statement of Investments [Line Items]
Available-for-sale Securities, Amortized Cost Basis	172,052	174,026
Available-for-sale Securities, Gross Unrealized Gains	36	0
Available-for-sale Securities, Gross Unrealized Losses	(17,578)	(24,687)
Available-for-sale Securities	$ 154,510	$ 149,339

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details

- Definition

For an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity. The held-to-maturity category is for those securities that the entity has the positive intent and ability to hold until maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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Reference 12: http://www.xbrl.org/2003/role/presentationRef

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+ Details

- Definition

This item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.

+ References+ Details

- Definition

As of the balance sheet date, the excess of fair value over carrying value (amortized cost) of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding gain.

+ References+ Details

- Definition

As of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss.

+ References+ Details