Goodwill and Intangible Assets - Intangible Asset Useful Life (Details)	12 Months Ended
	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period	3 years 6 days
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period	3 years 8 months 6 days
Non-compete agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period	2 years 8 months 6 days
Trademarks
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period	9 months 6 days
Acquired technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period	2 years 1 month 6 days
Assembled workforce
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	3 years
Weighted Average Amortization Period	2 years 1 month 6 days
Purchased software and licenses
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years
Weighted Average Amortization Period	4 years 6 months 6 days
Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	2 years
Minimum | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	4 years
Minimum | Non-compete agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	2 years
Minimum | Trademarks
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	2 years
Minimum | Acquired technology
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	3 years
Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	6 years
Maximum | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	6 years
Maximum | Non-compete agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years
Maximum | Trademarks
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	3 years
Maximum | Acquired technology
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years
Maximum | Purchased software and licenses
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years