Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

Schedule of assets measured at fair value on a recurring basis

The Company's assets that are measured at fair value on a recurring basis consist of the following:

			Fair Value Measurements at Reporting Date Using
As of September 30, 2019	Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Available-for-sale debt securities:
Corporate bonds	$	3,907.0	—		$	3,907.0
U.S. government and government agency obligations	66.0		—		66.0
Sovereign bonds	27.4		—		27.4
Commercial paper	108.8		—		108.8
Certificates of deposit	66.8		—		66.8
Equity securities (unrestricted)	46.9		$	46.9	—
Equity securities (restricted)	382.8		49.3		333.5
	$	4,605.7	$	96.2	$	4,509.5
As of December 31, 2018
Available-for-sale debt securities:
Corporate bonds	$	2,718.4	—		$	2,718.4
U.S. government and government agency obligations	109.4		—		109.4
Sovereign bonds	7.6		—		7.6
Commercial paper	113.8		—		113.8
Certificates of deposit	60.0		—		60.0
Equity securities (unrestricted)	43.6		$	43.6	—
Equity securities (restricted)	44.4		—		44.4
	$	3,097.2	$	43.6	$	3,053.6