Fair Values of Assets Held by Japanese and Foreign Plans (Detail) (JPY ¥) In Millions, unless otherwise specified	Mar. 31, 2012		Mar. 31, 2011		Mar. 31, 2010
Japanese plans
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	¥ 556,247		¥ 536,648		¥ 515,701
Japanese plans | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	142,504		150,843
Japanese plans | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	346,662		320,696
Japanese plans | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	67,081		65,109		74,490
Japanese plans | Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	58,862	[1]	63,693	[1]
Japanese plans | Commingled funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	58,862	[1]	63,693	[1]
Japanese plans | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	14,586		25,151
Japanese plans | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	14,586		25,151
Japanese plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	130,283	[2]	127,695	[2]
Japanese plans | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	127,918	[2]	125,692	[2]
Japanese plans | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	2,365	[2]	2,003	[2]
Japanese plans | Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	255,010	[3]	226,183	[3]
Japanese plans | Government bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	255,010	[3]	226,183	[3]
Japanese plans | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	23,853	[4]	23,375	[4]
Japanese plans | Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	23,853	[4]	23,375	[4]
Japanese plans | Asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	4,722	[5]	3,451	[5]
Japanese plans | Asset-backed securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	4,722	[5]	3,451	[5]
Japanese plans | Commodity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	1,850	[6]	1,991	[6]
Japanese plans | Commodity Funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	1,850	[6]	1,991	[6]
Japanese plans | Private equity
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	23,388	[7]	19,888	[7]
Japanese plans | Private equity | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	23,388	[7]	19,888	[7]	21,337
Japanese plans | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	42,258	[8]	43,688	[8]
Japanese plans | Hedge funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	42,258	[8]	43,688	[8]	51,498
Japanese plans | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	1,435		1,533
Japanese plans | Real estate | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	1,435		1,533		1,655
Foreign plans
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	151,139		140,387		134,226
Foreign plans | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	31,393		34,178
Foreign plans | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	110,702		97,060
Foreign plans | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	9,044		9,149		8,951
Foreign plans | Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	43,902	[9]	50,517	[9]
Foreign plans | Commingled funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	43,902	[9]	49,987	[9]
Foreign plans | Commingled funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held			530	[9]	528
Foreign plans | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	859		860
Foreign plans | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	859		860
Foreign plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	36,497	[10]	38,512	[10]
Foreign plans | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	30,514	[10]	33,273	[10]
Foreign plans | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	5,983	[10]	5,239	[10]
Foreign plans | Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	43,504	[11]	21,405	[11]
Foreign plans | Government bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	43,504	[11]	21,405	[11]
Foreign plans | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	9,192	[12]	14,994	[12]
Foreign plans | Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	5,231	[12]	10,148	[12]
Foreign plans | Corporate bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	3,961	[12]	4,846	[12]	4,571
Foreign plans | Asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	648		2,053
Foreign plans | Asset-backed securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	648		2,053
Foreign plans | Asset-backed securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held					75
Foreign plans | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	9,283	[13]	6,718	[13]
Foreign plans | Insurance contracts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	9,283	[13]	6,718	[13]
Foreign plans | Real estate and other
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	7,254	[14]	5,328	[14]
Foreign plans | Real estate and other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	20	[14]	45	[14]
Foreign plans | Real estate and other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	2,151	[14]	1,510	[14]
Foreign plans | Real estate and other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of the assets held	¥ 5,083	[14]	¥ 3,773	[14]	¥ 3,777

[1] Commingled funds represent pooled institutional investments, including primarily investment trusts. They include approximately 39 percent and 42 percent of investments in equity, 58 percent and 56 percent of investments in fixed income, and 3 percent and 2 percent of investments in other for the fiscal years ended March 31, 2011 and 2012, respectively.

[2] Includes approximately 64 percent and 65 percent of Japanese equity securities, and 36 percent and 35 percent of foreign equity securities for the fiscal years ended March 31, 2011 and 2012, respectively.

[3] Includes approximately 65 percent and 64 percent of debt securities issued by Japanese national and local governments, and 35 percent and 36 percent of debt securities issued by foreign national and local governments for the fiscal years ended March 31, 2011 and 2012, respectively.

[4] Includes debt securities issued by Japanese and foreign corporation and government related agencies.

[5] Includes primarily mortgage-backed securities.

[6] Represents commodity futures funds.

[7] Includes multiple private equity funds of funds that primarily invest in venture, buyout, and distressed markets in the U.S. and Europe.

[8] Includes primarily funds that invest in a portfolio of a broad range of hedge funds to diversify the risks and reduce the volatilities associated with a single hedge fund.

[9] Commingled funds represent pooled institutional investments including mutual funds, common trust funds, and collective investment funds. They are primarily comprised of foreign equities and fixed income investments.

[10] Includes primarily foreign equity securities.

[11] Includes primarily foreign government debt securities.

[12] Includes primarily foreign corporate debt securities.

[13] Represents annuity contracts with or without profit sharing.

[14] Includes primarily private real estate investment trusts.