Revenue Revenue (Impact of Adoption of Topic 606) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net of allowances	$ 353,749		$ 322,892
Inventories, net	338,767		309,060
Contract assets	36,613		0
Costs in excess of billings on uncompleted contracts	0		28,738
Prepaid expenses and other current assets	55,055		57,949
Total assets	1,543,508		1,473,350
Accrued expenses and other liabilities	83,052		96,262
Contract liabilities	29,089		0
Billings in excess of costs on uncompleted contracts	0		18,428
Total liabilities	779,933		726,451
Total liabilities and stockholders' equity	1,543,508		$ 1,473,350
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net of allowances		$ 314,008
Inventories, net		305,932
Contract assets		38,557
Costs in excess of billings on uncompleted contracts		0
Prepaid expenses and other current assets		61,077
Total assets		1,474,285
Accrued expenses and other liabilities		89,295
Contract liabilities		26,330
Billings in excess of costs on uncompleted contracts		0
Total liabilities		727,386
Total liabilities and stockholders' equity		1,474,285
Balances without adoption of Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net of allowances	361,631
Inventories, net	342,735
Contract assets	0
Costs in excess of billings on uncompleted contracts	26,912
Prepaid expenses and other current assets	51,087
Total assets	1,541,689
Accrued expenses and other liabilities	89,700
Contract liabilities	0
Billings in excess of costs on uncompleted contracts	20,622
Total liabilities	778,114
Total liabilities and stockholders' equity	1,541,689
Adoption of Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net of allowances	(7,882)	(8,884)
Inventories, net	(3,968)	(3,128)
Contract assets	36,613	38,557
Costs in excess of billings on uncompleted contracts	(26,912)	(28,738)
Prepaid expenses and other current assets	3,968	3,128
Total assets	1,819	935
Accrued expenses and other liabilities	(6,648)	(6,967)
Contract liabilities	29,089	26,330
Billings in excess of costs on uncompleted contracts	(20,622)	(18,428)
Total liabilities	1,819	935
Total liabilities and stockholders' equity	$ 1,819	$ 935