Condensed Consolidated Statements Of Partners' Capital (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 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	38,188	24,388
Cash distributions	(67,445)	(52,189)
Issuance of common units for cash, units	5,750,000
Issuance of common units for cash, value	169,421
Conversion of waiver units, units	1,738,000
Conversion of waiver units, value	0
Other, units	12,000
Other, value	500
Partners' capital, June 30, units	79,464,519	64,615,000
Partners' capital, June 30, value	$ 933,302	$ 641,463