Equity Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010		Aug. 31, 2010
Condensed Financial Statements, Captions [Line Items]
Equity investments	$ 65,882		$ 107,047
Muskegon Pipeline LLC
Condensed Financial Statements, Captions [Line Items]
Ownership	40.00%		40.00%
Equity investments	14,302		14,552
Transport4, LLC
Condensed Financial Statements, Captions [Line Items]
Ownership	25.00%		25.00%
Equity investments	481		341
West Shore Pipe Line Company
Condensed Financial Statements, Captions [Line Items]
Ownership	34.60%	[1]	34.60%	[1]	24.90%
Equity investments	44,987	[1]	43,563	[1]
South Portland Terminal LLC
Condensed Financial Statements, Captions [Line Items]
Ownership	50.00%	[2]	50.00%	[2]
Equity investments	6,112	[2]
West Texas LPG Pipeline Limited Partnership
Condensed Financial Statements, Captions [Line Items]
Equity investments			$ 48,591	[3]

[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.

[3] In May 2011, we sold our 20.0% interest. See Note 3 for further information.