Equity-based Awards (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Equity-based compensation expense [Abstract]
Total compensation expense	$ 18.0		$ 14.2		$ 53.8		$ 47.1
Restricted Common Unit Awards [Member]
Equity-based compensation expense [Abstract]
Total compensation expense	17.8		13.8		52.7		44.3
Unit Option Awards [Member]
Equity-based compensation expense [Abstract]
Total compensation expense	0.1		0.2		0.7		1.2
Other Equity-based Awards [Member]
Equity-based compensation expense [Abstract]
Total compensation expense	$ 0.1	[1]	$ 0.2	[1]	$ 0.4	[1]	$ 1.6	[1]
Long-Term Incentive Plan (1998) [Member]
Equity-based compensation expense [Abstract]
Remaining number of common units available to be issued as awards (in units)	1,151,778				1,151,778
Long-Term Incentive Plan (2008) [Member]
Equity-based compensation expense [Abstract]
Incremental number of units to be authorized annually (in units)					2,500,000
Maximum number of additional units to be authorized for issuance (in units)					35,000,000
Maximum number of common units that may be issued as awards (in units)	10,000,000				10,000,000
Remaining number of common units available to be issued as awards (in units)	4,333,287				4,333,287

[1] Primarily represents expense associated with unit appreciation rights ("UARs"), phantom units and similar awards.