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

9 Months Ended

Sep. 30, 2013

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

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

September 30, 2013	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Estimated Fair Value
U.S. Treasury securities	$	1,017.2	$	0.7	$	—		$	1,017.9
U.S. government-sponsored agency securities	400.1		0.2		(0.9		)	399.4
U.S. government-sponsored agency MBS	587.1		0.5		(7.9		)	579.7
Non-U.S. government, agency and Supranational securities	74.2		—		(0.1		)	74.1
Corporate debt - global	701.8		0.9		(1.2		)	701.5
Asset backed securities	229.6		0.1		(0.3		)	229.4
Marketable equity securities	190.7		231.6		—			422.3
Total available-for-sale marketable securities	$	3,200.7	$	234.0	$	(10.4	)	$	3,424.3

December 31, 2012	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Estimated Fair Value
U.S. Treasury securities	$	902.0	$	0.5	$	—		$	902.5
U.S. government-sponsored agency securities	303.5		0.3		—			303.8
U.S. government-sponsored agency MBS	387.2		1.6		(1.8		)	387.0
Non-U.S. government, agency and Supranational securities	7.1		—		—			7.1
Corporate debt - global	208.5		0.9		(0.2		)	209.2
Marketable equity securities	0.4		—		(0.1		)	0.3
Total available-for-sale marketable securities	$	1,808.7	$	3.3	$	(2.1	)	$	1,809.9

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

	Amortized Cost		Fair Value
Duration of one year or less	$	1,370.4	$	1,369.3
Duration of one through three years	1,419.0		1,415.7
Duration of three through five years	203.7		200.4
Duration of over five years	16.9		16.6
Total	$	3,010.0	$	3,002.0