XML 102 R69.htm IDEA: XBRL DOCUMENT v3.8.0.1

Benefit Plans Components of Benefit Plans (Details)	6 Months Ended
	Mar. 31, 2018 plans
Retirement Plan Disclosure
Number of defined benefit plans	1
Number of unfunded post-retirement health care plans	2

X

- Definition

The number of qualified defined benefit pension plans.

+ References

No definition available.

+ Details

Name:	tve_NumberOfQualifiedDefinedBenefitPlans
Namespace Prefix:	tve_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The number of unfunded post-retirement health care plans that provide for non-vested contributions toward the cost of certain retirees' medical coverage.

+ References

No definition available.

+ Details

Name:	tve_NumberOfUnfundedPostRetirementHealthCarePlans
Namespace Prefix:	tve_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration