Expense Example (Mid Cap Stock Trust, USD $)	12 Months Ended
May 01, 2011
Series I, Mid Cap Stock Trust
Expense Example:
Year 1	$ 95
Year 3	296
Year 5	515
Year 10	1,143
Series II, Mid Cap Stock Trust
Expense Example:
Year 1	115
Year 3	359
Year 5	622
Year 10	1,375
Series NAV, Mid Cap Stock Trust
Expense Example:
Year 1	90
Year 3	281
Year 5	488
Year 10	$ 1,084

Name:	rr_ExpenseExampleAbstract
Namespace Prefix:	rr
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.

+ References

Reference 1: 1
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 3
-Paragraph 4
-Subsection instructions

+ Details

Name:	rr_ExpenseExampleYear01
Namespace Prefix:	rr
Data Type:	rr:NonNegativeMonetaryType
Balance Type:	na
Period Type:	duration

- Definition

+ References

Reference 1: 1
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 3
-Paragraph 1
-Subparagraph 2
-Subsection example

+ Details

Name:	rr_ExpenseExampleYear03
Namespace Prefix:	rr
Data Type:	rr:NonNegativeMonetaryType
Balance Type:	na
Period Type:	duration

- Definition

+ References

Reference 1: 1
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 3
-Paragraph 1
-Subparagraph 2
-Subsection example

+ Details

Name:	rr_ExpenseExampleYear05
Namespace Prefix:	rr
Data Type:	rr:NonNegativeMonetaryType
Balance Type:	na
Period Type:	duration

- Definition

+ References

Reference 1: 1
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 3
-Paragraph 1
-Subparagraph 2
-Subsection example

+ Details

Name:	rr_ExpenseExampleYear10
Namespace Prefix:	rr
Data Type:	rr:NonNegativeMonetaryType
Balance Type:	na
Period Type:	duration