Summary of Significant Accounting Policies - Revenue and Expense Recognition (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) claim	Dec. 31, 2018 claim	Dec. 31, 2017 claim
Disaggregation of Revenue [Line Items]
Minimum amount of insurance coverage	$ 2,000
Maximum amount of insurance coverage	10,000
Average amount of insurance coverage	$ 3,300
Number of claims made | claim	9,059	8,091	6,214
Management Services Agreements (MSA) | Minimum
Disaggregation of Revenue [Line Items]
Contract term	3 years
Management Services Agreements (MSA) | Maximum
Disaggregation of Revenue [Line Items]
Contract term	5 years