Investments - Additional Information (Detail) (JPY ¥) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of Investments [Line Items]
Gross realized gains	¥ 204	¥ 641	¥ 277
Gross realized losses	4,281	1,961	2,482
Investments in affiliated companies accounted for by the equity method	15,776	26,817
Canon's share of net earnings (losses) in affiliated companies accounted for by the equity method, included in other income (deductions)	(7,368)	10,471	(12,649)
Time deposits with original maturities of more than three months	125,497	95,814
Aggregate cost of non-marketable equity securities accounted for under the cost method	14,583	26,475
Aggregate cost of investments not evaluated for impairment	¥ 14,583	¥ 24,053

This element represents the aggregate carrying amount of all cost-method investments held by the Company. Generally, such investments do not have readily determinable fair values and are not required to be accounted for by the equity method. The carrying amount of such securities equates to cost, adjusted for other-than-temporary impairment. The cost method and lower-of-cost or market, an adaptation of the cost method, is generally followed for most investments in noncontrolled corporations, in some corporate joint ventures, and to a lesser extent in unconsolidated subsidiaries, particularly foreign.

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- Definition

This element represents the aggregate carrying amount of all cost-method investments held by the Entity which was not evaluated for impairment. Because the fair value of cost-method investments is not readily determinable, the evaluation of whether an investment is impaired generally consists of whether an event or change in circumstances has occurred during the reporting period that may have a significant adverse effect on the fair value of the investment (an "impairment indicator"). Impairment indicators include, but are not limited to: (1) significant deterioration in the earnings performance, credit rating, asset quality, or business prospects of the investee; (2) significant adverse change in the regulatory, economic, or technological environment of the investee; (3) significant adverse change in the general market condition of either the geographic area or the industry in which the investee operates; (4) a bona fide offer to purchase (whether solicited or unsolicited), an offer by the investee to sell, or a completed auction process for the same or similar security for an amount less than the cost of the investment; or (5) factors that raise significant concerns about the investee's ability to continue as a going concern, such as negative cash flows from operations, working capital deficiencies, or noncompliance with statutory capital requirements or debt covenants.

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- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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