New Accounting Pronouncements New Accounting Pronouncements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in tax expense due to GILTI										$ 710
Services	$ 393,662	$ 375,830	$ 379,743	$ 326,968	$ 402,747	$ 375,800	$ 390,532	$ 344,700		1,476,203	$ 1,513,779	$ 1,385,785
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification										(1,170)
Payment for Contingent Consideration Liability, Operating Activities										29,141	42,790	44,914
Net Cash Provided by (Used in) Operating Activities										17,280	71,786	(45,907)
Payment for Contingent Consideration Liability, Investing Activities										61,313	99,873	135,693
Cost of Goods and Services Sold	256,088	$ 238,690	$ 253,390	$ 243,030	268,673	$ 249,418	$ 267,822	$ 237,563		991,198	1,023,476	936,133
Operating Income (Loss)										9,696	131,959	48,431
Net Income (Loss) Available to Common Stockholders, Basic										$ (132,088)	205,594	(45,839)
Earnings Per Share, Basic and Diluted										$ (2.31)
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Services										$ 1,527,839
Cost of Goods and Services Sold										1,053,556
Operating Income (Loss)										(1,026)
Net Income (Loss) Available to Common Stockholders, Basic										$ (138,971)
Earnings Per Share, Basic and Diluted										$ (2.43)
Accounting Standards Update 2016-18 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted Cash	$ 3,900				$ 4,600					$ 3,900	4,600	5,300
Accounting Standards Update 2016-15 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities										(29)	$ (42,790)	$ (44,914)
Accounting Standards Update 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Services										51,636
Cost of Goods and Services Sold										62,358
Operating Income (Loss)										(10,722)
Net Income (Loss) Available to Common Stockholders, Basic										$ (6,883)
Earnings Per Share, Basic and Diluted										$ (0.12)
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification									$ (1,170)	$ (1,170)