Gas Stored Underground And Gas Receivables And Payables (Details) (USD $)	9 Months Ended
Sep. 30, 2012 TBTU	Dec. 31, 2011 TBTU
Gas Held for Storage [Member]
Gas Stored Underground and Gas Receivables and Payable [Line Items]
Gas Held For Storage On Behalf Of Customers ( in TBtu)	124.5	118.0
Value of gas held on behalf of others	$ 346,100,000
Average market price of gas assumed during the period (in dollars per MMBtu)	2.78
Gas Loaned to Customers [Member]
Gas Stored Underground and Gas Receivables and Payable [Line Items]
The volume of gas owed to operating subsidiaries due to imbalances and gas loaned under PAL and no-notice agreements (in TBtu)	8.4	9.5
Average market price of gas assumed during the period (in dollars per MMBtu)	2.78
Market value of gas owed to operating subsidiaries due to gas imbalances and gas loaned under PAL and no-notice services	$ 23,400,000

This element represents the average price per share of gas for the period under review.

No definition available.

Name:	bwp_AssumedAverageMarketPrice
Namespace Prefix:	bwp_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of natural gas stored underground as of balance sheet date, in depleted gas reservoirs, aquifers, or salt caverns to meet seasonal and peak load demands, and also as insurance against unforeseen supply disruptions, which is owned by third parties and not recorded on the Company's Condensed Consolidated Balance Sheet.

+ References

No definition available.

+ Details

Name:	bwp_GasHeldForStorageOnBehalfOfCustomers
Namespace Prefix:	bwp_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	instant

- Definition

The value of gas balancing asset or liability as of the end of the period

+ References

No definition available.

+ Details

Name:	bwp_GasImbalanceToSubsidiariesAssetLiability
Namespace Prefix:	bwp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	bwp_GasStoredUndergroundAndGasReceivablesAndPayableLineItems
Namespace Prefix:	bwp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The market value of gas held in storage on behalf of its customers. This is not recognized in the financial statements because the Partnership does not own the gas - it is a market risk, however.

+ References

No definition available.

+ Details

Name:	bwp_MarketValueOfGasHeldOnBehalfOfCustomers
Namespace Prefix:	bwp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of the gas imbalance in terms of units of measure (Mcf) as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 10

-Section S99

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=21918352&loc=d3e512571-122862

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 90-22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_GasImbalanceVolumeAmount
Namespace Prefix:	us-gaap_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	instant