Assets and Liabilities Measured at Fair Value (Detail) (JPY ¥) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Assets:
Cash and cash equivalents	¥ 204,307	¥ 249,907
Derivatives	4,718	11,950
Total assets	229,303	289,213
Liabilities:
Derivatives	2,610	913
Total liabilities	2,610	913
Corporate Bonds
Assets:
Available-for-sale (current)	20	1,000
Available-for-sale (noncurrent)	558	994
Government Bond
Assets:
Available-for-sale (current)		1
Available-for-sale (noncurrent)	150	161
Fund Trusts
Assets:
Available-for-sale (noncurrent)	1,826	1,798
Equity Securities
Assets:
Available-for-sale (noncurrent)	17,724	23,402
Fair Value, Inputs, Level 1
Assets:
Total assets	18,045	23,574
Fair Value, Inputs, Level 1 \| Corporate Bonds
Assets:
Available-for-sale (current)	20
Fair Value, Inputs, Level 1 \| Government Bond
Assets:
Available-for-sale (current)		1
Available-for-sale (noncurrent)	150	161
Fair Value, Inputs, Level 1 \| Fund Trusts
Assets:
Available-for-sale (noncurrent)	151	10
Fair Value, Inputs, Level 1 \| Equity Securities
Assets:
Available-for-sale (noncurrent)	17,724	23,402
Fair Value, Inputs, Level 2
Assets:
Cash and cash equivalents	204,307	249,907
Derivatives	4,718	11,950
Total assets	210,804	263,689
Liabilities:
Derivatives	2,610	913
Total liabilities	2,610	913
Fair Value, Inputs, Level 2 \| Corporate Bonds
Assets:
Available-for-sale (noncurrent)	104	44
Fair Value, Inputs, Level 2 \| Fund Trusts
Assets:
Available-for-sale (noncurrent)	1,675	1,788
Fair Value, Inputs, Level 3
Assets:
Total assets	454	1,950
Fair Value, Inputs, Level 3 \| Corporate Bonds
Assets:
Available-for-sale (current)		1,000
Available-for-sale (noncurrent)	¥ 454	¥ 950

Investments in debt and equity securities which are categorized neither as trading securities nor held-to-maturity securities and which are intended be sold or mature within one year from the balance sheet date or the normal operating cycle, whichever is longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

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+ Details

- Definition

Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Glossary Available-for-Sale Securities

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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 includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

+ References+ Details

- Definition

Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

+ References+ Details

- Definition

Derivative instrument obligations meeting the definition of a liability which the Company is a party to as of the balance sheet date.

+ References+ Details