Selected Quarterly Financial Data - Unaudited (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues	$ 315,523	$ 307,471	$ 312,282	$ 330,932	$ 340,378	$ 327,169	$ 360,460	$ 372,033	$ 1,266,208	$ 1,400,040	$ 1,292,613
Gross Profit	114,140	118,552	103,869	135,303	134,640	134,587	151,800	149,001	471,864	570,028	426,095
Net Income	$ 20,641	$ 26,563	$ 22,833	$ 30,998	$ (7,355)	$ 219	$ 31,054	$ 4,875	$ 101,035	$ 28,793	$ 68,644
Basic	$ 1.00	$ 1.29	$ 1.11	$ 1.51	$ (0.36)	$ 0.01	$ 1.53	$ 0.24	$ 4.90	$ 1.41	$ 3.50
Diluted	$ 0.96	$ 1.24	$ 1.06	$ 1.44	$ (0.36)	$ 0.01	$ 1.44	$ 0.23	$ 4.69	$ 1.33	$ 3.29
Restructuring, strategic transaction and integration expenses					$ 41,100				$ 80,574	$ 105,390	$ 77,967
Contractsettlements					$ 8,600				$ 5,737	$ 41,613	$ 0