Guarantor Infromation (Balance Sheet) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
ASSETS
Cash and cash equivalents	$ 11,930	$ 11,610	$ 13,409	$ 6,927
Accounts receivable - affiliates	0	0
Accounts receivable - trade	81,997	80,568
Inventories	164,424	156,111
Prepaid expenses and other current assets	24,345	21,665
Current assets of discontinued operations	42,616	60,979
Total current assets	325,312	330,933
Investment in affiliates	0	0
Net property, plant and equipment	506,748	508,855
Deferred income taxes	19,340	19,803
Goodwill	171,117	171,117
Notes receivable - affiliate	0	0
Other assets	126,756	141,568
Total assets	1,149,273	1,172,276
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable - affiliate	0	0
Accounts payable - trade	47,253	47,663
Short-term debt	8,007	8,852
Accrued income and other taxes	7,539	5,256
Other accrued liabilities	27,279	30,594
Short-term liabilities of discontinued operations	16,168	20,042
Total current liabilities	106,246	112,407
Long-term debt - affiliate	0	0
Long-term debt - third party	367,956	356,580
Other long-term obligations	81,140	82,148
Deferred income taxes	45,707	42,906
Long-term liabilities of discontinued operations	971	850
Total stockholders' equity	547,253	577,385
Total liabilities and stockholders’ equity	1,149,273	1,172,276
Consolidating Entries and Eliminations
ASSETS
Cash and cash equivalents	0	0	0	0
Accounts receivable - affiliates	(75,407)	(74,859)
Accounts receivable - trade	0	0
Inventories		0
Prepaid expenses and other current assets	0	0
Current assets of discontinued operations	(2,063)	(4,477)
Total current assets	(77,470)	(79,336)
Investment in affiliates	(1,409,825)	(1,445,976)
Net property, plant and equipment	0	0
Deferred income taxes	0	0
Goodwill	0	0
Notes receivable - affiliate	(60,101)	(49,003)
Other assets	0	0
Total assets	(1,547,396)	(1,574,315)
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable - affiliate	(75,407)	(74,859)
Accounts payable - trade	0	0
Short-term debt	0	0
Accrued income and other taxes	0	0
Other accrued liabilities	0	0
Short-term liabilities of discontinued operations	(2,063)	(4,477)
Total current liabilities	(77,470)	(79,336)
Long-term debt - affiliate	(60,101)	(49,003)
Long-term debt - third party	0	0
Other long-term obligations	0	0
Deferred income taxes	0	0
Long-term liabilities of discontinued operations	0	0
Total stockholders' equity	(1,409,825)	(1,445,976)
Total liabilities and stockholders’ equity	(1,547,396)	(1,574,315)
Parent
ASSETS
Cash and cash equivalents	0	0	0	0
Accounts receivable - affiliates	51,592	51,592
Accounts receivable - trade	0	0
Inventories	0	0
Prepaid expenses and other current assets	554	1,350
Current assets of discontinued operations	0	0
Total current assets	52,146	52,942
Investment in affiliates	828,394	844,379
Net property, plant and equipment	0	0
Deferred income taxes	0	0
Goodwill	0	0
Notes receivable - affiliate		0
Other assets	0	0
Total assets	880,540	897,321
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable - affiliate	814	806
Accounts payable - trade	0	964
Short-term debt	0	0
Accrued income and other taxes	0	0
Other accrued liabilities	2,444	2,444
Short-term liabilities of discontinued operations	0	0
Total current liabilities	3,258	4,214
Long-term debt - affiliate	52,688	41,590
Long-term debt - third party	277,341	274,132
Other long-term obligations	0	0
Deferred income taxes	0	0
Long-term liabilities of discontinued operations	0	0
Total stockholders' equity	547,253	577,385
Total liabilities and stockholders’ equity	880,540	897,321
Guarantors
ASSETS
Cash and cash equivalents	811	636	736	646
Accounts receivable - affiliates	14,331	3,624
Accounts receivable - trade	9,705	7,518
Inventories	45,037	44,563
Prepaid expenses and other current assets	5,786	4,853
Current assets of discontinued operations	32,839	51,160
Total current assets	108,509	112,354
Investment in affiliates	581,431	601,597
Net property, plant and equipment	183,901	191,503
Deferred income taxes	0	0
Goodwill	70,399	70,399
Notes receivable - affiliate	60,101	49,003
Other assets	64,577	70,767
Total assets	1,068,918	1,095,623
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable - affiliate	61,074	71,243
Accounts payable - trade	7,701	8,033
Short-term debt	7,863	3,062
Accrued income and other taxes	1,405	2,095
Other accrued liabilities	7,986	12,205
Short-term liabilities of discontinued operations	14,622	20,381
Total current liabilities	100,651	117,019
Long-term debt - affiliate	0	0
Long-term debt - third party	89,778	81,695
Other long-term obligations	48,151	50,943
Deferred income taxes	1,158	909
Long-term liabilities of discontinued operations	786	678
Total stockholders' equity	828,394	844,379
Total liabilities and stockholders’ equity	1,068,918	1,095,623
Non-Guarantors
ASSETS
Cash and cash equivalents	11,119	10,974	$ 12,673	$ 6,281
Accounts receivable - affiliates	9,484	19,643
Accounts receivable - trade	72,292	73,050
Inventories	119,387	111,548
Prepaid expenses and other current assets	18,005	15,462
Current assets of discontinued operations	11,840	14,296
Total current assets	242,127	244,973
Investment in affiliates	0	0
Net property, plant and equipment	322,847	317,352
Deferred income taxes	19,340	19,803
Goodwill	100,718	100,718
Notes receivable - affiliate	0	0
Other assets	62,179	70,801
Total assets	747,211	753,647
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable - affiliate	13,519	2,810
Accounts payable - trade	39,552	38,666
Short-term debt	144	5,790
Accrued income and other taxes	6,134	3,161
Other accrued liabilities	16,849	15,945
Short-term liabilities of discontinued operations	3,609	4,138
Total current liabilities	79,807	70,510
Long-term debt - affiliate	7,413	7,413
Long-term debt - third party	837	753
Other long-term obligations	32,989	31,205
Deferred income taxes	44,549	41,997
Long-term liabilities of discontinued operations	185	172
Total stockholders' equity	581,431	601,597
Total liabilities and stockholders’ equity	$ 747,211	$ 753,647