Revenue Recognition (Schedule of Consolidated Statement of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
OPERATING ACTIVITIES
Net income	$ 30,306	$ 1,233	$ 40,788	$ 12,207
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	17,114	15,201	35,416	29,845
Amortization	2,559	2,632	5,205	5,281
Change in other noncurrent liabilities	(854)	(758)	(1,231)	(2,354)
Change in deferred taxes and other liabilities	(6,118)	(6,745)	(6,902)	(7,357)
Provision for write-off of property, plant and equipment	853	534	1,124	830
Non-cash interest expense	154	212	154	423
Compensation and benefits paid or payable in Class A Common Stock	1,047	681	1,336	1,670
Fair value adjustment on foreign currency option	34	75	71	129
Changes in operating assets and liabilities that (used)/provided cash:
Accounts receivable	(12,903)	(14,395)	(44,370)	(15,136)
Contract assets	(13,877)		(11,761)
Inventories	(1,371)	1,655	(10,615)	(13,266)
Prepaid expenses and other current assets	(1,157)	(780)	(5,220)	(2,697)
Income taxes prepaid and receivable	(5)	(2,817)	97	(2,817)
Accounts payable	11,420	(1,459)	8,882	2,065
Accrued liabilities	5,853	10,071	4,668	(900)
Income taxes payable	10,020	1,978	6,589	(508)
Noncurrent receivables	(1,643)	(3,621)	(4,170)	(7,536)
Other, net	(5,745)	4,692	(3,321)	3,938
Net cash provided by operating activities	35,687	8,389	16,740	3,817
Net cash used in investing activities	(23,375)	(21,713)	(39,175)	(46,796)
Net cash (used in)/provided by financing activities	(1,112)	10,207	(3,570)	(998)
Effect of exchange rate changes on cash and cash equivalents	(7,882)	(1,424)	(2,978)	1,027
(Decrease)/increase in cash and cash equivalents	3,318	(4,541)	(28,983)	(42,950)
Cash and cash equivalents at beginning of period	151,426	143,333	183,727	181,742
Cash and cash equivalents at end of period	154,744	$ 138,792	154,744	$ 138,792
As reported [Member]
OPERATING ACTIVITIES
Net income	30,306		40,788
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	17,114		35,416
Amortization	2,559		5,205
Change in other noncurrent liabilities	(854)		(1,231)
Change in deferred taxes and other liabilities	(6,118)		(6,902)
Provision for write-off of property, plant and equipment	853		1,124
Non-cash interest expense	154		154
Compensation and benefits paid or payable in Class A Common Stock	1,047		1,336
Fair value adjustment on foreign currency option	34		71
Changes in operating assets and liabilities that (used)/provided cash:
Accounts receivable	(12,903)		(44,370)
Contract assets	(13,877)		(11,761)
Inventories	(1,371)		(10,615)
Prepaid expenses and other current assets	(1,157)		(5,220)
Income taxes prepaid and receivable	(5)		97
Accounts payable	11,420		8,882
Accrued liabilities	5,853		4,668
Income taxes payable	10,020		6,589
Noncurrent receivables	(1,643)		(4,170)
Other, net	(5,745)		(3,321)
Net cash provided by operating activities	35,687		16,740
Net cash used in investing activities	(23,375)		(39,175)
Net cash (used in)/provided by financing activities	(1,112)		(3,570)
Effect of exchange rate changes on cash and cash equivalents	(7,882)		(2,978)
(Decrease)/increase in cash and cash equivalents	3,318		(28,983)
Cash and cash equivalents at beginning of period	151,426		183,727
Cash and cash equivalents at end of period	154,744		154,744
Adjustments to reverse effects of ASC 606 [Member]
OPERATING ACTIVITIES
Net income	(1,402)		(2,649)
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation
Amortization
Change in other noncurrent liabilities
Change in deferred taxes and other liabilities	(507)		(1,108)
Provision for write-off of property, plant and equipment
Non-cash interest expense
Compensation and benefits paid or payable in Class A Common Stock
Fair value adjustment on foreign currency option
Changes in operating assets and liabilities that (used)/provided cash:
Accounts receivable	(14,277)		(3,727)
Contract assets	13,877		11,761
Inventories	2,304		(4,222)
Prepaid expenses and other current assets
Income taxes prepaid and receivable
Accounts payable
Accrued liabilities	5		(55)
Income taxes payable
Noncurrent receivables
Other, net
Net cash provided by operating activities
Net cash used in investing activities
Net cash (used in)/provided by financing activities
Effect of exchange rate changes on cash and cash equivalents
(Decrease)/increase in cash and cash equivalents
Cash and cash equivalents at beginning of period
Cash and cash equivalents at end of period
As adjusted to exclude adoption of ASC 606 [Member]
OPERATING ACTIVITIES
Net income	28,904		38,139
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	17,114		35,416
Amortization	2,559		5,205
Change in other noncurrent liabilities	(854)		(1,231)
Change in deferred taxes and other liabilities	(6,625)		(8,010)
Provision for write-off of property, plant and equipment	853		1,124
Non-cash interest expense	154		154
Compensation and benefits paid or payable in Class A Common Stock	1,047		1,336
Fair value adjustment on foreign currency option	34		71
Changes in operating assets and liabilities that (used)/provided cash:
Accounts receivable	(27,180)		(48,097)
Contract assets
Inventories	933		(14,837)
Prepaid expenses and other current assets	(1,157)		(5,220)
Income taxes prepaid and receivable	(5)		97
Accounts payable	11,420		8,882
Accrued liabilities	5,858		4,613
Income taxes payable	10,020		6,589
Noncurrent receivables	(1,643)		(4,170)
Other, net	(5,745)		(3,321)
Net cash provided by operating activities	35,687		16,740
Net cash used in investing activities	(23,375)		(39,175)
Net cash (used in)/provided by financing activities	(1,112)		(3,570)
Effect of exchange rate changes on cash and cash equivalents	(7,882)		(2,978)
(Decrease)/increase in cash and cash equivalents	3,318		(28,983)
Cash and cash equivalents at beginning of period	151,426		183,727
Cash and cash equivalents at end of period	$ 154,744		$ 154,744