Leases (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Lease Cost [Abstract]
Operating lease cost	$ 3.9	$ 7.9
Short-term lease cost	0.1	0.2
Total	$ 4.0	8.1
Operating cash flows information [Abstract]
Cash paid for amounts included in the measurement of lease liabilities		8.3
Non-cash activity [Abstract]
Right-of-use assets obtained in the exchange for operating lease liabilities		$ 3.3
Weighted Average Remaining Lease Term and Discount Rates [Abstract]
Weighted-average remaining operating lease term	7 years 9 months 18 days	7 years 9 months 18 days
Weighted-average operating leases discount rate	5.00%	5.00%
Outstanding Lease Assets and Liabilities [Abstract]
Right-of-use asset	$ 47.1	$ 47.1
Lease liability - current	12.0	12.0
Lease liability - non-current	46.1	46.1
Future Minimum Lease Payments [Abstract]
For the remainder of 2019	7.7	7.7
2020	13.0	13.0
2021	9.6	9.6
2022	7.7	7.7
2023	6.2	6.2
Thereafter	26.3	26.3
Total future minimum lease payments	70.5	70.5
Less imputed interest	(12.6)	(12.6)
Total	$ 57.9	$ 57.9
Minimum Lease Payments under Non-cancellable Operating Leases [Abstract]
2019			$ 17.3
2020			13.0
2021			9.5
2022			8.2
2023			7.0
Thereafter			24.8
Total			79.8
Rent Expense [Abstract]
Rent expense			$ 19.5	$ 19.3
Minimum [Member]
Operating Leases [Abstract]
Remaining lease terms		1 year
Maximum [Member]
Operating Leases [Abstract]
Remaining lease terms		50 years