Summary of Significant Accounting Policies - Finite-Lived Intangible Assets (Details)	12 Months Ended
	Dec. 31, 2018
Customer Lists | Minimum
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (years)	8 years
Customer Lists | Maximum
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (years)	25 years
Developed technology | Minimum
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (years)	5 years
Developed technology | Maximum
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (years)	10 years
Tradenames | Minimum
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (years)	5 years
Tradenames | Maximum
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (years)	20 years
Noncompete Agreements | Maximum
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (years)	5 years