Revenue Recognition (Schedule of Consolidated Statement of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
OPERATING ACTIVITIES
Net income	$ 10,482	$ 10,974
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	18,302	14,644
Amortization	2,646	2,649
Change in other noncurrent liabilities	(377)	(1,596)
Change in deferred taxes and other liabilities	(784)	(612)
Provision for write-off of property, plant and equipment	271	296
Non-cash interest expense		211
Compensation and benefits paid or payable in Class A Common Stock	289	989
Fair value adjustment on foreign currency option	37	54
Changes in operating assets and liabilities that (used)/provided cash:
Accounts receivable	(31,467)	(741)
Contract assets	2,116
Inventories	(9,244)	(14,921)
Prepaid expenses and other current assets	(4,063)	(1,917)
Income taxes prepaid and receivable	102
Accounts payable	(2,538)	3,524
Accrued liabilities	(1,185)	(10,971)
Income taxes payable	(3,431)	(2,486)
Noncurrent receivables	2,527	(3,915)
Other, net	(2,630)	(754)
Net cash used in operating activities	(18,947)	(4,572)
Net cash used in investing activities	(15,800)	(25,083)
Net cash used in financing activities	(2,458)	(11,205)
Effect of exchange rate changes on cash and cash equivalents	4,904	2,451
Decrease in cash and cash equivalents	(32,301)	(38,409)
Cash and cash equivalents at beginning of period	183,727	181,742
Cash and cash equivalents at end of period	151,426	$ 143,333
As reported [Member]
OPERATING ACTIVITIES
Net income	10,482
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	18,302
Amortization	2,646
Change in other noncurrent liabilities	(377)
Change in deferred taxes and other liabilities	(784)
Provision for write-off of property, plant and equipment	271
Non-cash interest expense
Compensation and benefits paid or payable in Class A Common Stock	289
Fair value adjustment on foreign currency option	37
Changes in operating assets and liabilities that (used)/provided cash:
Accounts receivable	(31,467)
Contract assets	2,116
Inventories	(9,244)
Prepaid expenses and other current assets	(4,063)
Income taxes prepaid and receivable	102
Accounts payable	(2,538)
Accrued liabilities	(1,185)
Income taxes payable	(3,431)
Noncurrent receivables	2,527
Other, net	(2,630)
Net cash used in operating activities	(18,947)
Net cash used in investing activities	(15,800)
Net cash used in financing activities	(2,458)
Effect of exchange rate changes on cash and cash equivalents	4,904
Decrease in cash and cash equivalents	(32,301)
Cash and cash equivalents at beginning of period	183,727
Cash and cash equivalents at end of period	151,426
Adjustments to reverse effects of ASC 606 [Member]
OPERATING ACTIVITIES
Net income	(1,247)
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	1,103
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	7,324
Contract assets	(2,116)
Inventories	(8,023)
Prepaid expenses and other current assets
Income taxes prepaid and receivable
Accounts payable
Accrued liabilities	(250)
Income taxes payable
Noncurrent receivables
Other, net	3,209
Net cash used in operating activities
Net cash used in investing activities
Net cash used in financing activities
Effect of exchange rate changes on cash and cash equivalents
Decrease 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	9,235
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	18,302
Amortization	2,646
Change in other noncurrent liabilities	(377)
Change in deferred taxes and other liabilities	319
Provision for write-off of property, plant and equipment	271
Non-cash interest expense
Compensation and benefits paid or payable in Class A Common Stock	289
Fair value adjustment on foreign currency option	37
Changes in operating assets and liabilities that (used)/provided cash:
Accounts receivable	(24,143)
Contract assets
Inventories	(17,267)
Prepaid expenses and other current assets	(4,063)
Income taxes prepaid and receivable	102
Accounts payable	(2,538)
Accrued liabilities	(1,435)
Income taxes payable	(3,431)
Noncurrent receivables	2,527
Other, net	579
Net cash used in operating activities	(18,947)
Net cash used in investing activities	(15,800)
Net cash used in financing activities	(2,458)
Effect of exchange rate changes on cash and cash equivalents	4,904
Decrease in cash and cash equivalents	(32,301)
Cash and cash equivalents at beginning of period	183,727
Cash and cash equivalents at end of period	$ 151,426