Summary of Significant Accounting Policies - Significant Estimates Used by Management in Determining Fair Values of Customer Relationships Acquired (Details) |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
Minimum | |||
Goodwill And Intangible Assets [Line Items] | |||
Discount rates | 20.00% | 17.00% | 20.00% |
Customer attrition rates | 20.00% | 15.00% | 10.00% |
Maximum | |||
Goodwill And Intangible Assets [Line Items] | |||
Discount rates | 27.00% | 25.00% | 23.00% |
Customer attrition rates | 33.00% | 78.00% | 70.00% |