Fair Value Measurements Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Level 1 [Member]
Mortgages Held-for-sale, Fair Value Disclosure	$ 0	$ 0
Available-for-sale Securities, Fair Value Disclosure	49,420	50,873
Other Assets, Fair Value Disclosure	15,863	15,259
Assets, Fair Value Disclosure	65,283	66,132
Liabilities, Fair Value Disclosure	15,249	15,524
Level 1 [Member] \| Equity Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	49,420	50,873
Level 1 [Member] \| U.S. Government Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] \| U.S. Government-Sponsored Agency Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] \| State and Municipal Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] \| Corporate Debt Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] \| Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] \| Mortgage-Backed Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 1 [Member] \| Auction Rate Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 2 [Member]
Mortgages Held-for-sale, Fair Value Disclosure	63,045	67,899
Available-for-sale Securities, Fair Value Disclosure	2,521,592	2,511,536
Other Assets, Fair Value Disclosure	11,503	14,710
Assets, Fair Value Disclosure	2,596,140	2,594,145
Liabilities, Fair Value Disclosure	7,052	8,161
Level 2 [Member] \| Equity Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 2 [Member] \| U.S. Government Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	325	325
Level 2 [Member] \| U.S. Government-Sponsored Agency Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	894	2,397
Level 2 [Member] \| State and Municipal Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	295,193	315,519
Level 2 [Member] \| Corporate Debt Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	103,318	102,555
Level 2 [Member] \| Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Fair Value Disclosure	1,305,799	1,211,119
Level 2 [Member] \| Mortgage-Backed Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	816,063	879,621
Level 2 [Member] \| Auction Rate Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member]
Mortgages Held-for-sale, Fair Value Disclosure	0	0
Available-for-sale Securities, Fair Value Disclosure	166,365	159,626
Other Assets, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure	166,365	159,626
Liabilities, Fair Value Disclosure	0	0
Level 3 [Member] \| Equity Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] \| U.S. Government Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] \| U.S. Government-Sponsored Agency Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] \| State and Municipal Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] \| Corporate Debt Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	11,726	10,287
Level 3 [Member] \| Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] \| Mortgage-Backed Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	0	0
Level 3 [Member] \| Auction Rate Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	154,639	149,339
Total [Member]
Mortgages Held-for-sale, Fair Value Disclosure	63,045	67,899
Available-for-sale Securities, Fair Value Disclosure	2,737,377	2,722,035
Other Assets, Fair Value Disclosure	27,366	29,969
Assets, Fair Value Disclosure	2,827,788	2,819,903
Liabilities, Fair Value Disclosure	22,301	23,685
Total [Member] \| Equity Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	49,420	50,873
Total [Member] \| U.S. Government Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	325	325
Total [Member] \| U.S. Government-Sponsored Agency Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	894	2,397
Total [Member] \| State and Municipal Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	295,193	315,519
Total [Member] \| Corporate Debt Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	115,044	112,842
Total [Member] \| Collateralized Mortgage Obligations [Member]
Available-for-sale Securities, Fair Value Disclosure	1,305,799	1,211,119
Total [Member] \| Mortgage-Backed Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	816,063	879,621
Total [Member] \| Auction Rate Securities [Member]
Available-for-sale Securities, Fair Value Disclosure	$ 154,639	$ 149,339

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References+ Details