Earnings from Equity Investments (Parenthetical) (Detail)							1 Months Ended
	Dec. 31, 2011 West Shore Pipe Line Company		Dec. 31, 2010 West Shore Pipe Line Company		Aug. 31, 2010 West Shore Pipe Line Company	May 31, 2011 West Texas LPG Pipeline Limited Partnership	Jul. 31, 2011 South Portland Terminal LLC	Dec. 31, 2011 South Portland Terminal LLC		Dec. 31, 2010 South Portland Terminal LLC
Condensed Financial Statements, Captions [Line Items]
Ownership	34.60%	[1]	34.60%	[1]	24.90%			50.00%	[2]	50.00%	[2]
Percentage of ownership interest sold						20.00%
Percentage of ownership interest acquired							50.00%

[1] In August 2010, we acquired additional shares, which increased our interest from 24.9% to 34.6%. See Note 3 for further information.

[2] In July 2011, we acquired a 50.0% interest. See Note 3 for further information.