Amortized Costs and Fair Values (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Equity securities, Amortized costs	$ 10,870	$ 10,870
Total, Amortized costs	498,631	481,083
Debt securities, Fair values	509,897
Equity securities, Fair values	12,153	11,073
Available for sale securities, Total	522,050	503,259
Municipal
Schedule of Available-for-sale Securities [Line Items]
Debt securities, Amortized costs	38,312	18,012
Debt securities, Fair values	38,625	19,011
Corporate and utilities
Schedule of Available-for-sale Securities [Line Items]
Debt securities, Amortized costs	269,246	268,874
Debt securities, Fair values	287,484	287,528
Foreign
Schedule of Available-for-sale Securities [Line Items]
Debt securities, Amortized costs	165,860	168,084
Debt securities, Fair values	168,166	169,009
U.S. Government
Schedule of Available-for-sale Securities [Line Items]
Debt securities, Amortized costs	14,343	15,243
Debt securities, Fair values	$ 15,622	$ 16,638

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

Amount of debt securities categorized neither as held-to-maturity nor trading.

+ References

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+ Details

- Definition

Amount of equity securities categorized neither as held-to-maturity nor as trading.

+ References

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+ Details

- 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