Leases - Additional Information (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019 Agreement	Dec. 31, 2018 USD ($)
Lessee Lease Description [Line Items]
Number of sublease agreements | Agreement	2
Total cash receipts from subleases | $		$ 23.7
Minimum
Lessee Lease Description [Line Items]
Remaining lease terms	1 year
Maximum
Lessee Lease Description [Line Items]
Remaining lease terms	6 years