Equity-based Awards (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Equity-based compensation expense [Abstract]
Total compensation expense	$ 17.2		$ 16.4
Restricted Common Unit Awards [Member]
Equity-based compensation expense [Abstract]
Total compensation expense	16.6		14.8
Unit Option Awards [Member]
Equity-based compensation expense [Abstract]
Total compensation expense	0.4		0.7
Other Equity-based Awards [Member]
Equity-based compensation expense [Abstract]
Total compensation expense	$ 0.2	[1]	$ 0.9	[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)	877,049
Long-Term Incentive Plan (2008) [Member]
Equity-based compensation expense [Abstract]
Remaining number of common units available to be issued as awards (in units)	4,247,819

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