Subsequent Events (Details) (USD $)	0 Months Ended									1 Months Ended	9 Months Ended		12 Months Ended
	Nov. 14, 2011		Aug. 12, 2011	May 13, 2011	Feb. 14, 2011	Nov. 12, 2010	Aug. 13, 2010	May 14, 2010	Feb. 12, 2010	Oct. 31, 2011	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Nov. 04, 2011	Nov. 03, 2011
Cash distribution declared date										October 2011	October 18, 2011
Per unit cash distribution amount	$ 0.8000	[1]	$ 0.7850	$ 0.7700	$ 0.7575	$ 0.7450	$ 0.7325	$ 0.7200	$ 0.7100	$ 0.800	$ 2.3125	$ 2.1625	$ 3.1125	$ 2.9075
Cash distribution paid date	11/14/2011(a)	[1]	8/12/2011	5/13/2011	2/14/2011	11/12/2010	8/13/2010	5/14/2010	2/12/2010	November 14, 2011	Through 9/30/2011	Through 9/30/2010
Cash distribution record date										November 1, 2011	November 1, 2011
Total cash distributions	$ 90,189,000	[1]	$ 88,498,000	$ 86,807,000	$ 85,398,000	$ 83,798,000	$ 82,393,000	$ 76,847,000	$ 75,779,000	$ 90,200,000	$ 260,703,000	$ 235,019,000	$ 350,892,000	$ 318,817,000
Property, plant and equipment, net of depreciation											3,225,931,000			3,178,556,000
Borrowing capacity										800,000,000	550,000,000
Line of credit facility maturity date										October 2016	September 2012
Accounts receivable from clearing agent															15,300,000	29,400,000
Amount transferred from one clearing agent to other															14,100,000
Ammonia Pipeline System [Member]
Property, plant and equipment, net of depreciation											$ 34,500,000
Maximum [Member]
Interest spread over LIBOR rate										1.75%	0.80%
Commitment fee, percent										0.30%	0.125%
Minimum [Member]
Interest spread over LIBOR rate										0.875%	0.30%
Commitment fee, percent										0.125%	0.05%

[1] Our general partner's board of directors declared this cash distribution on October 18, 2011 to be paid on November 14, 2011 to unitholders of record at the close of business on November 1, 2011.