Summary of Significant Accounting Policies - Recently Issued and Adopted Accounting Pronouncements - ASU 2016-02 (Details) - USD ($) $ in Millions		6 Months Ended
	Jan. 01, 2019	Jun. 30, 2019
Accounting Pronouncements
Lease, Practical Expedients, Package		true
Lease, Practical Expedient, Land Easement		true
Lease, Practical Expedient, Use of Hindsight		false
Right-of-use assets		$ 25.9
Lease liability		$ 27.2
ASU 2016-02
Accounting Pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	true
New Accounting Pronouncement or Change in Accounting Principle, Prior Period Not Restated	true
ASU 2016-02 | Adjustment
Accounting Pronouncements
Right-of-use assets	$ 23.9
Lease liability	$ 25.0