Related-Party Transactions, Summary of Transactions (Details) (USD $)	3 Months Ended						0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Tesoro		Mar. 31, 2013 Tesoro		Apr. 23, 2014 Subsequent Event
Related Party Transaction
Revenues	$ 109,580,000	$ 47,892,000	$ 109,580,000		$ 47,892,000
Operating and maintenance expenses			10,271,000	[1]	3,397,000	[1]
General and administrative expenses			7,480,000		2,826,000
Imbalance settlement gains	2,417,000	2,424,000	2,417,000		2,424,000
Cash distribution paid to Tesoro	16,300,000
Declaration date							Apr. 23, 2014
Cash distributions per unit (dollars per unit)	$ 0.5650	$ 0.4725					$ 0.5900
Distribution date	Feb. 13, 2014						May 15, 2014
Cash distribution declared to Tesoro	$ 23,129,000	$ 14,835,000					$ 18,100,000

[1] Operating and maintenance expenses include imbalance settlement gains of $2.4 million for both the three months ended March 31, 2014 and 2013.