Consolidated Statement of Partners' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Units	General Partner Interest	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest [Member]
Balance at Dec. 31, 2012	$ 452,856	$ 502,809	$ (145,877)	$ (4,279)	$ 100,203
Increase (Decrease) in Partners' Equity [Roll Forward]
Issuance of common units	73,444	73,444
Net income	42,586	29,753	11,870		963
Other comprehensive income (loss)	4,824			4,824
Contributions from general partner	1,499		1,499		0
Distributions to unitholders	(67,419)	(54,696)	(12,723)
Distributions made to joint venture partners	(2,000)				(2,000)
Purchase of units for restribted grants	(2,933)	(2,933)
Amortization of restricted and performance units	1,880	1,880
Class B Unit Accretion	(3,057)	(2,996)	(61)
Other	(513)		(513)
Balance at Jun. 30, 2013	$ 501,167	$ 547,261	$ (145,805)	$ 545	$ 99,166