Condensed Consolidated Statements Of Partners' Capital (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Statement of Partners' Capital [Abstract]
Partners' capital, January 1, units	71,965,062	64,615,000
Partners' capital, January 1, value	$ 792,638	$ 669,264
Net income	69,382	43,476
Cash distributions	(104,008)	(82,067)
Issuance of common units for cash, net, units	5,750,000	7,350,000
Issuance of common units for cash, net, value	169,421	184,969
Conversion of waiver units, units	3,476,000
Conversion of waiver units, value	0
Other, units	12,000
Other, value	500
Partners' capital, September 30, units	81,202,752	71,965,000
Partners' capital, September 30, value	$ 927,933	$ 815,642