Significant Accounting Policies - Cumulative Impact of Recently Adopted Accounting Standards (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid expenses and other current assets	$ 376.3	$ 266.7	$ 268.1
Property and equipment, net	830.9	908.8	951.7
Operating lease assets	169.7	192.5
Other long-term assets	514.6	404.8	403.5
Total assets	8,837.7	9,512.8	9,363.3
Other accrued liabilities	282.5	269.1	233.5
Long-term operating lease liabilities	158.1	185.5
Other long-term liabilities	58.1	53.1	119.8
Total liabilities	4,227.1	4,694.5	4,540.1
Accumulated deficit	$ (2,741.4)	(2,836.3)	$ (2,831.4)
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid expenses and other current assets		(1.4)
Property and equipment, net		(42.9)
Operating lease assets		192.5
Other long-term assets		1.3
Total assets		149.5
Other accrued liabilities		35.6
Long-term operating lease liabilities		185.5
Other long-term liabilities		(66.7)
Total liabilities		154.4
Accumulated deficit		$ (4.9)