Investments in Securities (Tables)

12 Months Ended

Mar. 31, 2011

Mar. 31, 2010

Cost, Fair Value, Gross Unrealized Gain (Losses) of Available-for-Sale Securities

	Yen (millions)
	2011
	Cost		Fair value		Gross unrealized holding gains		Gross unrealized holding losses
Noncurrent:
Equity securities		250,400		313,813		67,755		4,342
Corporate and government bonds		2,142		2,201		59		—
Other debt securities		544		546		8		6
		253,086		316,560		67,822		4,348
	Yen (millions)
	2010
	Cost		Fair value		Gross unrealized holding gains		Gross unrealized holding losses
Noncurrent:
Equity securities		275,579		379,358		104,666		887
Corporate and government bonds		3,894		3,961		75		8
Other debt securities		568		585		22		5
		280,041		383,904		104,763		900

Maturities of Investments in Available-for-Sale Securities

	Yen (millions)
	2011				2010
	Cost		Fair value		Cost		Fair value
Due after one year through five years		2,686		2,747		4,462		4,546
Equity securities		250,400		313,813		275,579		379,358
		253,086		316,560		280,041		383,904

Available For Sale Securities In Continuous Unrealized Loss Position [Member]

Gross Unrealized Holding Losses on Investments in Available-for-Sale Securities and Fair Value of Related Investments

	Yen (millions)
	2011
	Less than 12 months				12 months or more				Total
	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Equity securities		48,891		4,342		—		—		48,891		4,342
Other debt securities		35		6		—		—		35		6
		48,926		4,348		—		—		48,926		4,348

	Yen (millions)
	2010
	Less than 12 months				12 months or more				Total
	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Equity securities		6,222		887		—		—		6,222		887
Corporate and government bonds		1,194		8		—		—		1,194		8
Other debt securities		40		5		—		—		40		5
		7,456		900		—		—		7,456		900