Consolidated Statement of Partners' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Units	General Partner Interest	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2011	$ 329,377	$ 482,509	$ (146,668)	$ (6,464)
Increase (Decrease) in Partners' Equity [Roll Forward]
Net income	45,141	34,360	10,781
Other comprehensive income	685			685
Distributions to unitholders	(59,977)	(48,697)	(11,280)
Purchase of units for incentive grants	(4,005)	(4,005)
Amortization of restricted and performance units	1,629	1,629
Other	14		14
Balance at Jun. 30, 2012	$ 312,864	$ 465,796	$ (147,153)	$ (5,779)