Summary of Significant Accounting Policies - Leases (Details)	3 Months Ended
	Mar. 31, 2019
Leases
Operating lease - existence of option to extend	true
Finance lease - existence of option to extend	true
Minimum
Leases
Operating lease renewal term (in years)	2 years
Finance lease renewal term (in years)	2 years
Maximum
Leases
Operating term of lease (in years)	5 years
Operating lease renewal term (in years)	5 years
Finance term of lease (in years)	5 years
Finance lease renewal term (in years)	5 years