v3.3.1.900
Selected Quarterly Financial Information (Unaudited) (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Net sales $ 66,004 $ 49,325 $ 80,815 $ 93,050 $ 74,401 $ 66,733 $ 77,215 $ 80,316 $ 289,194 $ 298,665 $ 323,672
Operating costs and expenses:                      
Cost of product sold (exclusive of depreciation and amortization) 9,495 14,501 15,424 25,769 15,374 15,434 19,436 21,708 65,189 71,952 58,075
Direct operating expenses (exclusive of depreciation and amortization) 23,317 33,179 25,146 24,414 21,744 26,108 26,917 24,189 106,056 98,958 94,092
Selling, general and administrative expenses (exclusive of depreciation and amortization) 5,620 6,042 4,523 4,583 3,816 3,963 5,270 4,654 20,768 17,703 21,076
Depreciation and amortization 7,214 7,409 7,010 6,819 6,978 6,812 6,792 6,667 28,452 27,249 25,578
Total operating costs and expenses 45,646 61,131 52,103 61,585 47,912 52,317 58,415 57,218 220,465 215,862 198,821
Operating income 20,358 (11,806) 28,712 31,465 26,489 14,416 18,800 23,098 68,729 82,803 124,851
Interest expense and other financing costs (1,739) (1,727) (1,717) (1,697) (1,731) (1,724) (1,669) (1,659) (6,880) (6,783) (6,294)
Interest income 6 10 12 12 11 7 6 6 40 30 74
Other income, net 99 54 5 6 23 33 0 15 164 71 93
Total other income (expense) (1,634) (1,663) (1,700) (1,679) (1,697) (1,684) (1,663) (1,638) (6,676) (6,682) (6,127)
Income before income tax expense (benefit) 18,724 (13,469) 27,012 29,786 24,792 12,732 17,137 21,460 62,053 76,121 118,724
Income tax expense (benefit) (7) 9 (4) 12 (55) 13 7 7 11 (28) 108
Net income $ 18,731 $ (13,478) $ 27,016 $ 29,774 $ 24,847 $ 12,719 $ 17,130 $ 21,453 $ 62,042 $ 76,149 $ 118,616
Net income per common unit - basic (in dollars per unit) $ 0.26 $ (0.18) $ 0.37 $ 0.41 $ 0.34 $ 0.17 $ 0.23 $ 0.29 $ 0.85 $ 1.04 $ 1.62
Net income per common unit - diluted (in dollars per unit) $ 0.26 $ (0.18) $ 0.37 $ 0.41 $ 0.34 $ 0.17 $ 0.23 $ 0.29 $ 0.85 $ 1.04 $ 1.62
Weighted-average common units outstanding:                      
Basic (in units) 73,123 73,123 73,123 73,123 73,117 73,115 73,113 73,113 73,123 73,115 73,072
Diluted (in units) 73,131 73,123 73,131 73,131 73,133 73,139 73,146 73,145 73,131 73,139 73,228
Affiliates                      
Operating costs and expenses:                      
Cost of product sold (exclusive of depreciation and amortization) $ 1,552 $ 1,147 $ 2,184 $ 1,818 $ 2,619 $ 2,232 $ 2,327 $ 2,246 $ 6,701 $ 9,424 $ 10,791
Direct operating expenses (exclusive of depreciation and amortization) 841 1,030 1,195 1,027 833 621 817 753 4,093 3,024 4,072
Selling, general and administrative expenses (exclusive of depreciation and amortization) 3,672 3,661 3,361 3,267 2,867 3,035 3,973 3,536 13,961 13,411 16,118
Third parties                      
Operating costs and expenses:                      
Cost of product sold (exclusive of depreciation and amortization) 7,943 13,354 13,240 23,951 12,755 13,202 17,109 19,462 58,488 62,528 47,284
Direct operating expenses (exclusive of depreciation and amortization) 22,476 32,149 23,951 23,387 20,911 25,487 26,100 23,436 101,963 95,934 90,020
Selling, general and administrative expenses (exclusive of depreciation and amortization) $ 1,948 $ 2,381 $ 1,162 $ 1,316 $ 949 $ 928 $ 1,297 $ 1,118 $ 6,807 $ 4,292 $ 4,958