Fair Value Measurements Table (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure		$ 248,251
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	22,800
Totals
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	1,188,353
Estimate of Fair Value, Fair Value Disclosure [Member] \| US Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	7,155	7,891
Estimate of Fair Value, Fair Value Disclosure [Member] \| Obligations of U.S. states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	491,183	468,818
Estimate of Fair Value, Fair Value Disclosure [Member] \| Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	225,897	294,926
Estimate of Fair Value, Fair Value Disclosure [Member] \| Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	40,474	53,147
Estimate of Fair Value, Fair Value Disclosure [Member] \| Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	22,186	13,780
Estimate of Fair Value, Fair Value Disclosure [Member] \| Corporate and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	378,658
Estimate of Fair Value, Fair Value Disclosure [Member] \| Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure		21,080
Estimate of Fair Value, Fair Value Disclosure [Member] \| Totals
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure		1,107,893
Fair Value, Inputs, Level 1 [Member] \| US Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] \| Obligations of U.S. states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] \| Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] \| Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] \| Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] \| Corporate and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] \| Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	17,454	15,954
Fair Value, Inputs, Level 1 [Member] \| Totals
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	17,454	15,954
Fair Value, Inputs, Level 2 [Member] \| US Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	7,155	7,891
Fair Value, Inputs, Level 2 [Member] \| Obligations of U.S. states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	491,183	468,818
Fair Value, Inputs, Level 2 [Member] \| Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	225,897	294,926
Fair Value, Inputs, Level 2 [Member] \| Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	40,474	53,147
Fair Value, Inputs, Level 2 [Member] \| Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	22,186	13,780
Fair Value, Inputs, Level 2 [Member] \| Corporate and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	378,658	248,251
Fair Value, Inputs, Level 2 [Member] \| Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	5,126
Fair Value, Inputs, Level 2 [Member] \| Totals
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	1,165,553	1,091,939
Fair Value, Inputs, Level 3 [Member] \| US Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] \| Obligations of U.S. states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] \| Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] \| Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] \| Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] \| Corporate and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] \| Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	5,346	0
Fair Value, Inputs, Level 3 [Member] \| Totals
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Fair Value Disclosure	$ 5,346	$ 0

Fair Value Measurements Table (Details) (USD $)
In Thousands, unless otherwise specified

Dec. 31, 2012

Dec. 31, 2011

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

$ 248,251

Equity securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

22,800

Totals

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

1,188,353

Estimate of Fair Value, Fair Value Disclosure [Member] | US Treasury securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

7,155

7,891

Estimate of Fair Value, Fair Value Disclosure [Member] | Obligations of U.S. states and political subdivisions

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

491,183

468,818

Estimate of Fair Value, Fair Value Disclosure [Member] | Residential mortgage-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

225,897

294,926

Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial mortgage-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

40,474

53,147

Estimate of Fair Value, Fair Value Disclosure [Member] | Other asset-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

22,186

13,780

Estimate of Fair Value, Fair Value Disclosure [Member] | Corporate and other debt securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

378,658

Estimate of Fair Value, Fair Value Disclosure [Member] | Equity securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

21,080

Estimate of Fair Value, Fair Value Disclosure [Member] | Totals

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

1,107,893

Fair Value, Inputs, Level 1 [Member] | US Treasury securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 1 [Member] | Obligations of U.S. states and political subdivisions

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 1 [Member] | Residential mortgage-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 1 [Member] | Commercial mortgage-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 1 [Member] | Other asset-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 1 [Member] | Corporate and other debt securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 1 [Member] | Equity securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

17,454

15,954

Fair Value, Inputs, Level 1 [Member] | Totals

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

17,454

15,954

Fair Value, Inputs, Level 2 [Member] | US Treasury securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

7,155

7,891

Fair Value, Inputs, Level 2 [Member] | Obligations of U.S. states and political subdivisions

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

491,183

468,818

Fair Value, Inputs, Level 2 [Member] | Residential mortgage-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

225,897

294,926

Fair Value, Inputs, Level 2 [Member] | Commercial mortgage-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

40,474

53,147

Fair Value, Inputs, Level 2 [Member] | Other asset-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

22,186

13,780

Fair Value, Inputs, Level 2 [Member] | Corporate and other debt securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

378,658

248,251

Fair Value, Inputs, Level 2 [Member] | Equity securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

5,126

Fair Value, Inputs, Level 2 [Member] | Totals

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

1,165,553

1,091,939

Fair Value, Inputs, Level 3 [Member] | US Treasury securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 3 [Member] | Obligations of U.S. states and political subdivisions

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 3 [Member] | Residential mortgage-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 3 [Member] | Commercial mortgage-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 3 [Member] | Other asset-backed securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 3 [Member] | Corporate and other debt securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

Fair Value, Inputs, Level 3 [Member] | Equity securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

5,346

Fair Value, Inputs, Level 3 [Member] | Totals

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Available-for-sale Securities, Fair Value Disclosure

$ 5,346

$ 0

- 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