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Reconciliation for Level 3 Plan Assets (Detail)
In Millions
12 Months Ended 12 Months Ended
Mar. 31, 2011
USD ($)
Mar. 31, 2011
JPY (¥)
Mar. 31, 2010
JPY (¥)
Mar. 31, 2011
Level 3
USD ($)
Mar. 31, 2011
Level 3
JPY (¥)
Mar. 31, 2010
Level 3
JPY (¥)
Mar. 31, 2011
Level 3
Alternative Investments
Pooled Funds
USD ($)
Mar. 31, 2011
Level 3
Alternative Investments
Pooled Funds
JPY (¥)
Mar. 31, 2010
Level 3
Alternative Investments
Pooled Funds
JPY (¥)
Mar. 31, 2011
Alternative Investments
Pooled Funds
USD ($)
Mar. 31, 2011
Alternative Investments
Pooled Funds
JPY (¥)
Mar. 31, 2010
Alternative Investments
Pooled Funds
JPY (¥)
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]                        
Beginning Balance $ 1,033 ¥ 85,967 ¥ 74,111 $ 60 ¥ 4,948 ¥ 4,728 $ 57 [1] ¥ 4,728 [1] ¥ 3,514 $ 140 [1] ¥ 11,633 [1] ¥ 11,122 [1]
Realized and unrealized return on plan assets (5) (449) 9,382       3 220 453      
Purchases, sales and redemptions, net             0 0 761      
Ending Balance $ 1,027 ¥ 85,396 ¥ 85,967 $ 60 ¥ 4,948 ¥ 4,728 $ 60 [1] ¥ 4,948 [1] ¥ 4,728 [1] $ 140 [1] ¥ 11,633 [1] ¥ 11,122 [1]
[1] These funds invest in hedge funds as alternative investments.