Leases (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Lessee Lease Description [Line Items]
Operating lease option to terminate	within 1 year
Operating lease existence of option to terminate	true
Short-term leases term	12 months
Finance lease, liabilities	$ 0
Additional operating leases not yet commenced	no additional operating leases that have not yet commenced
Rent expense		$ 6,100,000
Minimum [Member]
Lessee Lease Description [Line Items]
Remaining lease term operating lease	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Remaining lease term operating lease	15 years
Lease renewal term operating lease	5 years