Accounting Policies - Leases (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Practical expedients - Package	true
Practical expedients - Hindsight	false
Operating right-of-use assets	$ 28.9
Operating lease liabilities	$ 28.9
ASU 2016-02 | Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating right-of-use assets		$ 33.6
Operating lease liabilities		$ 33.9