Equity-Based Awards, Restricted Unit Awards (Details) - Restricted Common Unit Awards [Member] - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate of restricted common unit awards		25.00%
Summary of awards activity, equity instruments other than options [Roll Forward]
Beginning of period (in units)		1,960,520		4,229,790	7,221,214
Vested (in units)		(1,234,502)		(2,009,970)	(2,634,074)
Forfeited (in units)		(43,724)		(259,300)	(357,350)
End of period (in units)		682,294	[1]	1,960,520	4,229,790
Restricted units outstanding, weighted-average grant date fair value [Roll Forward]
Weighted-average grant date fair value per unit, at beginning of period (in dollars per unit)	[2]	$ 27.88		$ 26.96	$ 25.83
Vested weighted-average grant date fair value per unit (in dollars per unit)	[2]	27.45		26.00	23.94
Forfeited weighted-average grant date fair value per unit (in dollars per unit)	[2]	28.48		27.53	26.38
Weighted-average grant date fair value per unit, at end of period (in dollars per unit)	[2]	$ 28.61		$ 27.88	$ 26.96
Summary of awards activity, equity instruments other than options, additional disclosures [Abstract]
Cash distributions paid to restricted common unitholders		$ 1.6		$ 4.0	$ 7.3
Total intrinsic value of restricted common unit awards that vested during period		28.5		$ 67.3	$ 87.1
Unrecognized Compensation Expense [Abstract]
Unrecognized compensation cost		$ 0.7
Long-Term Incentive Plan (2008) [Member]
Summary of awards activity, equity instruments other than options [Roll Forward]
End of period (in units)		491,280
Enterprise [Member]
Unrecognized Compensation Expense [Abstract]
Unrecognized compensation cost		$ 0.5

[1] Of the total number of restricted common units outstanding at December 31, 2016, a total of 491,280 were issued under the 2008 Plan with the balance issued under the 1998 Plan.

[2] Determined by dividing the aggregate grant date fair value of awards (before an allowance for forfeitures) by the number of awards issued.