3. Recent Accounting Pronouncements 3. Recent Accounting Pronouncements - Statement of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	$ 891,791	$ 876,068
Cost of sales	807,607	598,457
Gross profit	84,184	277,611
Operating income	(7,995)	179,921
Income before taxes and equity in earnings of unconsolidated affiliates	15,360	213,998
Income tax expense	(5,679)	(28,031)
Equity in earnings of unconsolidated affiliates, net of tax	(552)	9,669
Net income	9,129	195,636
Comprehensive income	$ 6,826	$ 207,250
Net income per share, basic	$ 0.09	$ 1.92
Net income per share, diluted	$ 0.09	$ 1.90
Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales		$ 848,484
Cost of sales		585,539
Gross profit		262,945
Operating income		165,255
Income before taxes and equity in earnings of unconsolidated affiliates		199,332
Income tax expense		(33,764)
Equity in earnings of unconsolidated affiliates, net of tax		4,997
Net income		170,565
Comprehensive income		$ 182,179
Net income per share, basic		$ 1.67
Net income per share, diluted		$ 1.66
Accounting Standards Update 2016-09 [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales		$ 0
Cost of sales		0
Gross profit		0
Operating income		0
Income before taxes and equity in earnings of unconsolidated affiliates		0
Income tax expense		7,909
Equity in earnings of unconsolidated affiliates, net of tax		0
Net income		7,909
Comprehensive income		$ 7,909
Net income per share, basic		$ 0.08
Net income per share, diluted		$ 0.08
Accounting Standards Update 2014-09 [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales		$ 27,584
Cost of sales		12,918
Gross profit		14,666
Operating income		14,666
Income before taxes and equity in earnings of unconsolidated affiliates		14,666
Income tax expense		(2,176)
Equity in earnings of unconsolidated affiliates, net of tax		4,672
Net income		17,162
Comprehensive income		$ 17,162
Net income per share, basic		$ 0.17
Net income per share, diluted		$ 0.16