Long-Term Incentive Plan (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Limited partners' capital account, units authorized for issuance	4,700,000
Limited partner unitholders, units remaining available	1,200,000
Minimum tax withholdings associated partner units with settlement	$ 13.0
Employer taxes paid	$ 1.3
General partner's board of directors approved units	131,687
2012 Awards [Member]
Limited partners' capital account, units authorized for issuance	361,383