Intangibles Assets and Goodwill - Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Jul. 12, 2017
Goodwill
Goodwill, beginning of the period			$ 373,291	$ 747,325	$ 373,291
Additions				5,580	406,522
Reductions				(44,427)	(32,787)
Currency translation adjustments				(220)	299
Goodwill, end of the period	$ 708,258	$ 747,325		708,258	747,325
Accumulated impairment losses	137,900			137,900
Impairment of goodwill				44,400
Impairment of goodwill and other intangible assets	48,127	69,437		48,127	69,437
Sale of Meridian Consulting Group, LLC			2,700
Novitex
Goodwill
Goodwill associated with deferred tax liabilities assumed						$ 46,991
ITPS
Goodwill
Goodwill, beginning of the period			159,394	566,215	159,394
Additions				5,580	406,522
Currency translation adjustments				(220)	299
Goodwill, end of the period	571,575	566,215		571,575	566,215
ITPS | Novitex
Goodwill
Additions					406,100
HS
Goodwill
Goodwill, beginning of the period			86,786	86,786	86,786
Goodwill, end of the period	86,786	86,786		86,786	86,786
LLPS
Goodwill
Goodwill, beginning of the period			$ 127,111	94,324	127,111
Reductions				(44,427)	(32,787)
Goodwill, end of the period	49,897	94,324		49,897	94,324
Impairment of goodwill	$ 44,400	$ 30,100		$ 44,400
Impairment of goodwill and other intangible assets					$ 30,100