Summary of Significant Accounting Policies (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jan. 31, 2012	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012
Cash Distributions [Abstract]
Subsequent Cash Distribution, Declaration Date			Aug. 02, 2012
Subsequent Cash Distribution, Amount			$ 22,100,000
Subsequent Cash Distribution, Distribution Declared (in dollars per unit)			$ 0.21
Subsequent Cash Distribution, Distribution Date			Aug. 30, 2012
Subsequent Cash Distribution, Date of Record			Aug. 13, 2012
Deferred Compensation Plans [Abstract]
Vesting period of awards					4 years
Employee allocation percentage maximum (in hundredths)	50.00%		50.00%		50.00%
Deferred cash maximum per employee	250,000		250,000		250,000
Deferred compensation liability for the full dollar value of the awards				159,900,000
Restricted Holding Unit Awards to Employees (in units)	2.7	8.7	2.8		11.9
Reclassified liability to partners' capital		130,300,000
One-time, non-cash deferred compensation charge				587,100,000
Percentage of unrecognized deferred incentive compensation expense recognized (in hundredths)				100.00%
Holding Units Purchased in Period (in units)			2.1		6.6
Dollar Amount Paid for Holding Units Acquired			28,200,000		95,100,000
Open-Market Purchases of Holding Units (in units)			2.1		6.3
Dollar Amount Paid for Open-Market Purchases of Holding Units			$ 27,500,000		$ 90,600,000
Unallocated Holding Units Remaining in the Consolidated Rabbi Trust (in holding units)	8.7		8.7		8.7