New Accounting Pronouncements (Condensed Consolidated Balance Sheet) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Condensed Consolidated Balance Sheets [Abstract]
Contract assets	$ 148,231	$ 146,496
Inventories, net	318,986	268,917
Prepaid expenses and other assets	35,277	36,018
Total Assets	2,037,185	2,109,304
Income taxes payable	20,803	11,663
Deferred income taxes	20,005	8,694
Total liabilities		770,166
Retained earnings	639,779	708,181
Total shareholders' equity	1,244,145	1,339,138
Total liabilities and shareholders' equity	$ 2,037,185	2,109,304
Accounting Standards Update 2014-09 [Member] | As Previously Reported [Member] | Calculated Under Revenue Guidance In Effect Before Topic 606 [Member]
Condensed Consolidated Balance Sheets [Abstract]
Contract assets		0
Inventories, net		397,181
Prepaid expenses and other assets		42,263
Total Assets		2,097,317
Income taxes payable		11,662
Deferred income taxes		7,027
Total liabilities		768,498
Retained earnings		697,862
Total shareholders' equity		1,328,819
Total liabilities and shareholders' equity		2,097,317
Accounting Standards Update 2014-09 [Member] | Restatement Adjustment [Member] | Adjustments [Member]
Condensed Consolidated Balance Sheets [Abstract]
Contract assets		146,496
Inventories, net		(128,264)
Prepaid expenses and other assets		(6,245)
Total Assets		11,987
Income taxes payable		1
Deferred income taxes		1,667
Total liabilities		1,668
Retained earnings		10,319
Total shareholders' equity		10,319
Total liabilities and shareholders' equity		$ 11,987