Partners' Capital And Distributions (Distributions) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																		12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2009		Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Partners' Capital And Distributions [Abstract]
Date Paid	February 2012		November 2011		August 2011		May 2011		February 2011		November 2010		August 2010		May 2010		February 2010
Per Unit Amount	$ 0.4400		$ 0.4275		$ 0.4150		$ 0.4075		$ 0.4000		$ 0.3875		$ 0.3750		$ 0.3675		$ 0.3600		$ 0.4400	$ 0.4000	$ 0.3600
Limited Partner Interests Amount	$ 31,664		$ 30,777		$ 29,878		$ 26,343		$ 25,846		$ 15,339		$ 14,845		$ 14,548		$ 14,251
General Partner Interest Amount		[1]		[1]		[1]		[1]		[1]	313	[1]	303	[1]	297	[1]	291	[1]
General Partner Incentive Distribution Amount		[1]		[1]		[1]		[1]		[1]	3,147	[1]	2,642	[1]	2,339	[1]	2,037	[1]		8,128	6,318
Total Amount	$ 31,664		$ 30,777		$ 29,878		$ 26,343		$ 25,846		$ 18,799		$ 17,790		$ 17,184		$ 16,579		$ (112,844)	$ (70,359)	$ (60,086)
General partners interest in cash distributions																				2.00%

[1] Prior to our IDR Restructuring in December 2010, our general partner received a 2% interest and incremental incentive cash distributions when unitholder's cash distributions exceeded certain target thresholds.