Accounting Policies - Leases (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 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	$ 31.2
Operating lease liabilities	$ 31.5
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