Fair Value Measurement (Details 1) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2011
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	$ 3,498,272
Level 2 [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	3,349,950
Issues	830
Level 2 [Member] \| U.S. government agency debentures [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	371,244
Issues	25
Level 2 [Member] \| U.S. States and political subdivisions [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	309,785
Issues	486
Level 2 [Member] \| Residential Mortgage Backed Securities Issued By US Government Sponsored Enterprises [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	1,588,971
Issues	208
Level 2 [Member] \| Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	1,079,947
Issues	110
Level 2 [Member] \| Non-agency [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	3
Issues	1
Level 2 [Member] \| Corporate debt securities [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	0
Issues	0
Level 3 [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	144,570
Issues	16
Level 3 [Member] \| U.S. government agency debentures [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	0
Issues	0
Level 3 [Member] \| U.S. States and political subdivisions [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	0
Issues	0
Level 3 [Member] \| Residential Mortgage Backed Securities Issued By US Government Sponsored Enterprises [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	0
Issues	0
Level 3 [Member] \| Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	3
Issues	1
Level 3 [Member] \| Non-agency [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	93,844
Issues	7
Level 3 [Member] \| Corporate debt securities [Member]
Fair value measurements from third party pricing service or independent brokers
Available for sale securities	$ 50,723
Issues	8

- 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