Cash, Cash Equivalents and Marketable Securities Available-for-Sale (Tables)

9 Months Ended

Sep. 30, 2015

Cash, Cash Equivalents, and Short-term Investments [Abstract]

Schedule of available-for-sale securities by major security type and class

The amortized cost, gross unrealized holding gains, gross unrealized holding losses and estimated fair value of available-for-sale securities by major security type and class of security at September 30, 2015 and December 31, 2014 were as follows:

September 30, 2015	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Estimated Fair Value
U.S. Treasury securities	$	92.8	$	—	$	—		$	92.8
U.S. government-sponsored agency MBS	34.0		—		(0.2		)	33.8
Corporate debt - global	213.4		0.2		(1.0		)	212.6
Asset backed securities	38.6		—		—			38.6
Marketable equity securities	820.3		365.8		(74.8		)	1,111.3
Total available-for-sale marketable securities	$	1,199.1	$	366.0	$	(76.0	)	$	1,489.1

December 31, 2014	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Estimated Fair Value
U.S. Treasury securities	$	1,044.7	$	0.3	$	(0.8	)	$	1,044.2
U.S. government-sponsored agency securities	145.1		0.1		(0.1		)	145.1
U.S. government-sponsored agency MBS	531.1		1.0		(2.7		)	529.4
Non-U.S. government, agency and Supranational securities	32.4		—		(0.1		)	32.3
Corporate debt - global	446.3		0.6		(1.2		)	445.7
Asset backed securities	177.3		—		(0.2		)	177.1
Marketable equity securities	335.2		716.3		(0.2		)	1,051.3
Total available-for-sale marketable securities	$	2,712.1	$	718.3	$	(5.3	)	$	3,425.1

Schedule of duration periods of available-for-sale debt securities

Duration periods of available-for-sale debt securities at September 30, 2015 were as follows:

	Amortized Cost		Fair Value
Duration of one year or less	$	68.1	$	67.9
Duration of one through three years	292.6		291.9
Duration of three through five years	18.1		18.0
Total	$	378.8	$	377.8