Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details 2) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts Receivable, net	$ 562,214,000				$ 653,484,000				$ 562,214,000	$ 653,484,000
Other Assets, Noncurrent	140,807,000				132,600,000				140,807,000	132,600,000
Other Liabilities, Current	6,495,000				3,395,000				6,495,000	3,395,000
Deferred Tax Liabilities, Net, Noncurrent	55,789,000				46,585,000				55,789,000	46,585,000
Retained Earnings (Accumulated Deficit)	(73,971,000)				(50,706,000)				(73,971,000)	(50,706,000)
Revenues	611,863,000	$ 633,996,000	$ 595,794,000	$ 661,609,000	606,806,000	$ 545,922,000	$ 473,089,000	$ 456,100,000	2,503,262,000	2,081,917,000	$ 1,332,164,000
Costs of products sold, exclusive of depreciation and amortization shown below									1,823,095,000
General and Administrative Expense									91,568,000	113,779,000	84,183,000
Income Tax Expense (Benefit)	6,531,000	(2,697,000)	(3,613,000)	23,083,000	31,141,000	(37,249,000)	3,625,000	95,000	23,304,000	(2,388,000)	11,268,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	2,972,000	8,461,000	(2,726,000)	(33,035,000)	$ 2,619,000	$ (19,103,000)	$ 9,611,000	$ (10,277,000)	(24,328,000)	(17,150,000)	13,262,000
Net Income (Loss) Available to Common Stockholders, Basic	$ (5,879,000)	$ 2,144,000	$ (8,937,000)	$ (37,867,000)					$ (50,539,000)	$ (17,150,000)	$ 2,095,000
Earnings Per Share, Basic	$ (0.08)	$ 0.03	$ (0.11)	$ (0.48)	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ (0.65)	$ (0.24)	$ 0.04
Earnings Per Share, Diluted	$ (0.08)	$ 0.03	$ (0.11)	$ (0.48)	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ (0.65)	$ (0.24)	$ 0.04
Accounting Standards Update 2014-09 [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Accounts Receivable, net	$ 562,057,000								$ 562,057,000
Other Assets, Noncurrent	119,911,000								119,911,000
Other Liabilities, Current	6,538,000								6,538,000
Deferred Tax Liabilities, Net, Noncurrent	50,045,000								50,045,000
Retained Earnings (Accumulated Deficit)	(89,324,000)								(89,324,000)
Revenues									2,483,962,000
Costs of products sold, exclusive of depreciation and amortization shown below									1,808,129,000
General and Administrative Expense									91,168,000
Income Tax Expense (Benefit)									23,209,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									(28,167,000)
Net Income (Loss) Available to Common Stockholders, Basic									$ (54,378,000)
Earnings Per Share, Basic									$ (0.70)
Earnings Per Share, Diluted									$ (0.70)
Accounting Standards Update 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Accounts Receivable, net	157,000								$ 157,000
Other Assets, Noncurrent	20,896,000								20,896,000
Other Liabilities, Current	(43,000)								(43,000)
Deferred Tax Liabilities, Net, Noncurrent	5,744,000								5,744,000
Retained Earnings (Accumulated Deficit)	$ 15,353,000								15,353,000
Revenues									19,300,000
Costs of products sold, exclusive of depreciation and amortization shown below									14,966,000
General and Administrative Expense									400,000
Income Tax Expense (Benefit)									95,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									3,839,000
Net Income (Loss) Available to Common Stockholders, Basic									$ 3,839,000
Earnings Per Share, Basic									$ 0.05
Earnings Per Share, Diluted									$ 0.05