CONDENSED CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL (USD $) In Thousands	Total	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests	Limited Partners	Class B Units
Beginning balance at Dec. 31, 2011	$ 2,323,957	$ (127,741)	$ 20,788	$ 2,035,271	$ 395,639
Net income	109,493		3,155	98,155	8,183
Credits associated with agreement and plan of merger	422			422
Distributions paid to unitholders	(185,449)		2,609	(188,058)
Net proceeds from issuance of units	246,648			246,648
Amortization of unit-based compensation awards	7,688			7,688
Proceeds from exercise of unit options	999			999
Payment of tax withholding on issuance of LTIP awards	(1,576)			(1,576)
Distributions paid to noncontrolling interests	(6,688)		(6,688)
Other comprehensive income (loss)	(22,618)	(22,618)
Noncash accrual for distribution equivalent rights	(433)			(433)
Other	657			657
Ending balance at Jun. 30, 2012	2,473,100	(150,359)	19,864	2,199,773	403,822
Beginning balance at Dec. 31, 2012	2,388,840	(158,779)	16,527	2,117,788	413,304
Net income	167,869		2,098	152,873	12,898
Acquisition of additional interest in WesPac Memphis	(9,727)		(1,495)	(8,232)
Distributions paid to unitholders	(201,242)		2,922	(204,164)
Net proceeds from issuance of units	372,824			372,824
Amortization of unit-based compensation awards	7,327			7,327
Proceeds from exercise of unit options	980			980
Payment of tax withholding on issuance of LTIP awards	(3,728)			(3,728)
Distributions paid to noncontrolling interests	(5,210)		(5,210)
Other comprehensive income (loss)	34,250	34,250
Noncash accrual for distribution equivalent rights	(667)			(667)
Other	31		41	(10)
Ending balance at Jun. 30, 2013	$ 2,751,547	$ (124,529)	$ 14,883	$ 2,434,991	$ 426,202