Supplemental Cash Flow Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Cash [Abstract]
Interest paid, net of capitalized interest	$ 23.7	[1]	$ 32.1	[1]
Income taxes paid, net of refunds	0.1		0.3
Non-cash:
Deadstock inventory transferred to property, plant and equipment	1.1		4.5
Accrued dividends on unvested equity awards	0.2		0.4
Change in receivables from unit offerings	5.9		0
Change in capital accruals	22.7		14.9
Transfers from materials and supplies inventory to property, plant and equipment	0.4		0
Change in ARO estimate	2.1		0.2
Interest capitalized on major projects	$ 6.9		$ 6.1

[1] Interest capitalized on major projects was $6.9 million and $6.1 million for the three months ended March 31, 2014 and 2013.