Available-For-Sale Securities Included in Short-Term Investments and Investments By Major Security Type (Detail) (JPY ¥) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Available for sale Securities Current
Schedule of Available-for-sale Securities [Line Items]
Cost		¥ 1,001
Fair value		1,001
Available for sale Securities Current \| Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Cost	20	1,000
Fair value	20	1,000
Available for sale Securities Current \| Government Bond
Schedule of Available-for-sale Securities [Line Items]
Cost		1
Fair value		1
Available for sale Securities Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Cost	18,519	21,266
Gross unrealized holding gains	3,275	5,830
Gross unrealized holding losses	1,536	741
Fair value	20,258	26,355
Available for sale Securities Noncurrent \| Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Cost	569	1,017
Gross unrealized holding gains	73	42
Gross unrealized holding losses	84	65
Fair value	558	994
Available for sale Securities Noncurrent \| Government Bond
Schedule of Available-for-sale Securities [Line Items]
Cost	172	183
Gross unrealized holding losses	22	22
Fair value	150	161
Available for sale Securities Noncurrent \| Fund Trusts
Schedule of Available-for-sale Securities [Line Items]
Cost	1,867	1,778
Gross unrealized holding gains	2	20
Gross unrealized holding losses	43
Fair value	1,826	1,798
Available for sale Securities Noncurrent \| Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	15,911	18,288
Gross unrealized holding gains	3,200	5,768
Gross unrealized holding losses	1,387	654
Fair value	¥ 17,724	¥ 23,402

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.

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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.

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- 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.

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