CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net sales	$ 81,411	$ 78,276
Operating costs and expenses:
Cost of product sold (exclusive of depreciation and amortization)	10,654	12,598
Direct operating expenses (exclusive of depreciation and amortization)	22,557	22,837
Selling, general and administrative expenses (exclusive of depreciation and amortization)	5,630	5,977
Depreciation and amortization	5,767	5,438
Total operating costs and expenses	44,608	46,850
Operating income	36,803	31,426
Other income (expense):
Interest expense and other financing costs (Note 12)	(1,280)	(1,203)
Interest income	30	33
Other income, net	9	6
Total other income (expense)	(1,241)	(1,164)
Income before income tax expense	35,562	30,262
Income tax expense	9	18
Net income	35,553	30,244
Net income per common unit-basic (in dollars per share)	$ 0.49	$ 0.41
Net income per common unit-diluted (in dollars per share)	$ 0.49	$ 0.41
Weighted-average common units outstanding:
Basic (in shares)	73,065	73,031
Diluted (in shares)	73,233	73,196
Affiliates
Operating costs and expenses:
Cost of product sold (exclusive of depreciation and amortization)	3,089	2,990
Direct operating expenses (exclusive of depreciation and amortization)	1,003	381
Selling, general and administrative expenses (exclusive of depreciation and amortization)	4,219	3,819
Third parties
Operating costs and expenses:
Cost of product sold (exclusive of depreciation and amortization)	7,565	9,608
Direct operating expenses (exclusive of depreciation and amortization)	21,554	22,456
Selling, general and administrative expenses (exclusive of depreciation and amortization)	$ 1,411	$ 2,158