v3.21.1

Offering Costs - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2021
Investment Holdings [Line Items]
Offering costs, amortization period	12 months

X

- Definition

Offering costs, amortization period, months.

+ References

No definition available.

+ Details

Name:	ck0001415311_OfferingCostsAmortizationPeriod
Namespace Prefix:	ck0001415311_
Data Type:	xbrli:durationItemType
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_InvestmentHoldingsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration