Long-term Incentive Compensation Plans (Details) (USD $)	1 Months Ended	3 Months Ended	6 Months Ended		1 Months Ended
	Jan. 31, 2013	Jun. 30, 2013	Jun. 30, 2013	Jun. 30, 2012	Jul. 01, 2013 Subsequent Event [Member]
Long-term Incentive Compensation Plans [Abstract]
Holding units purchased in period (in units)		300,000	1,300,000
Dollar amount paid for holding units acquired		$ 7,400,000	$ 27,000,000
Open-market purchases of holding units (in units)		300,000	1,100,000
Dollar amount paid for open-market purchases of holding units		7,200,000	23,200,000
Restricted holding unit awards to employees (in units)	6,500,000		6,800,000
Unallocated holding units remaining in the consolidated rabbi trust (in holding units)		13,100,000	13,100,000
Units issued upon options exercised (in units)			778,739
Proceeds from stock options exercised			$ 13,281,000	$ 0
Subsequent Event [Line Items]
Decrease in units shares outstanding (in holding units)					13,100,000