Summary of Significant Accounting Policies - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Cash payments for operating leases included in operating activities		$ 51.7
Cash payments for finance leases included in financing activities		1.3
Right-of-use assets obtained in exchange for lease obligations:
Operating leases	$ 8.2	51.1
Finance leases	$ 1.1	$ 1.5