Noncontrolling Interest Distribution and Other Payments to Noncontrolling Unitholders (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Distributions and Other Payments to Noncontrolling Unitholders [Line Items]
Distributions for taxes	$ 2,383	$ 4,812	$ 7,081
Other distributions	1,699	3,635	2,752
Payments Pursuant to the Tax Receivable Agreement	6,033	5,536	4,267
Distributions and other payments to noncontrolling unitholders, including TRA	10,115	13,983	14,100
Tax Distribution Rate	45.00%
TRA Savings Paid to Noncontrolling Unitholders	85.00%
Noncontrolling Interest Liability (Current and Non-Current)	148,081
Due to noncontrolling unitholders, current portion	$ 7,623	$ 6,209
Number of Years TRA Payments Expected to be Mad	15 years