Segment Information (Net Revenues By Geographic Area) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 242,638	$ 237,052	$ 245,768	$ 238,855	$ 266,716	$ 247,209	$ 259,658	$ 239,887	$ 964,313	$ 1,013,470	$ 505,492
United States
Segment Reporting Information [Line Items]
Revenues									412,686	430,575	234,684
France
Segment Reporting Information [Line Items]
Revenues									49,724	48,344	41,584
Germany
Segment Reporting Information [Line Items]
Revenues									96,232	97,526	32,092
Canada
Segment Reporting Information [Line Items]
Revenues									25,963	33,531	15,715
Saudi Arabia [Member]
Segment Reporting Information [Line Items]
Revenues									11,562	9,643	6,260
United Kingdom
Segment Reporting Information [Line Items]
Revenues									36,760	35,869	25,217
China
Segment Reporting Information [Line Items]
Revenues									32,779	35,732	15,056
Norway
Segment Reporting Information [Line Items]
Revenues									23,045	15,009	10,803
Europe [Member]
Segment Reporting Information [Line Items]
Revenues									111,852	101,787	48,849
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Revenues									96,711	86,261	44,816
Other Countries [Member]
Segment Reporting Information [Line Items]
Revenues									$ 66,999	$ 119,193	$ 30,416