Quarterly report pursuant to Section 13 or 15(d)

Acquisitions - Estimated Fair Values of Identifiable Intangible Assets and Related Weighted Average Amortization (Detail)

v3.10.0.1
Acquisitions - Estimated Fair Values of Identifiable Intangible Assets and Related Weighted Average Amortization (Detail) - USD ($)
$ in Thousands
9 Months Ended 12 Months Ended
Sep. 30, 2018
Sep. 30, 2018
Business Acquisition [Line Items]    
Estimated fair value at acquisition date   $ 52,400
Acquisitions 2018    
Business Acquisition [Line Items]    
Estimated fair value at acquisition date $ 52,364  
Weighted average amortization period at acquisition date 7 years 4 months 24 days  
Customer relationships | Acquisitions 2018    
Business Acquisition [Line Items]    
Estimated fair value at acquisition date $ 30,767  
Weighted average amortization period at acquisition date 5 years 3 months 18 days  
Backlog | Acquisitions 2018    
Business Acquisition [Line Items]    
Estimated fair value at acquisition date $ 2,158  
Weighted average amortization period at acquisition date 1 year  
Trade names | Acquisitions 2018    
Business Acquisition [Line Items]    
Estimated fair value at acquisition date $ 7,689  
Weighted average amortization period at acquisition date 15 years  
Non-compete agreements | Acquisitions 2018    
Business Acquisition [Line Items]    
Estimated fair value at acquisition date $ 2,750  
Weighted average amortization period at acquisition date 5 years  
Curriculum | Acquisitions 2018    
Business Acquisition [Line Items]    
Estimated fair value at acquisition date $ 9,000  
Weighted average amortization period at acquisition date 10 years