|
Commitments and Contingencies - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified |
Aug. 28, 2008
Total Bond Market Fund Litigation
|
Mar. 31, 2013
Margin Requirements
|
Mar. 31, 2013
Collateral Requirements
|
|---|---|---|---|
| Commitments and Contingencies Disclosure [Line Items] | |||
| Aggregate face amount of letter of credit agreements | $ 225 | $ 104 | |
| Alleged minimum percentage of fund assets invested in CMOs and mortgage-backed securities without obtaining shareholder vote | 25.00% |