Lease (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Mar. 31, 2019
Operating Leased Assets [Line Items]
Operating lease liabilities		$ 0
Operating lease right to use assets		0
Operating lease liability not yet commenced with obligations		$ 2,400,000
Operating leases rent expense	$ 25,300,000
Minimum [Member]
Operating Leased Assets [Line Items]
Operating lease, term		3 years
Lease terms, not yet commenced		1 year
Maximum [Member]
Operating Leased Assets [Line Items]
Operating lease, term		10 years
Lease terms, not yet commenced		5 years