Income Taxes, Deferred Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating loss carry-forwards	$ 23.8	$ 1.0
Research and other credit carry-forwards	137.5	128.7
Deferred revenue	125.6	109.3
Stock-based compensation	52.3	49.1
Cost sharing adjustment	69.9	70.1
Reserves and accruals not currently deductible	141.3	173.9
Other	12.8	19.2
Total deferred tax assets	563.2	551.3
Valuation allowance	(154.4)	(146.2)
Deferred tax assets, net of valuation allowance	408.8	405.1
Deferred tax liabilities:
Property and equipment basis differences	(58.1)	(44.1)
Purchased intangibles	(28.8)	(3.1)
Unremitted foreign earnings	(311.4)	(290.0)
Deferred compensation and other	(11.0)	(12.0)
Total deferred tax liabilities	409.3	349.2
Net deferred tax (liabilities) assets		55.9
Net deferred tax (liabilities) assets	(0.5)
Valuation allowance	154.4	146.2
Increase (decrease) in DTA valuation allowance	8.2	$ 1.7
Cumulative undistributed earnings of certain foreign subsidiaries	2,400.0
Federal [Member]
Deferred tax liabilities:
Net operating loss carry-forwards	55.9
Tax credit carry-forwards	2.7
California [Member]
Deferred tax liabilities:
Net operating loss carry-forwards	111.4
Tax credit carry-forwards	246.5
Tax credit carry-forward to be credited to APIC when realized	20.8
California Deferred Tax Assets [Member]
Deferred tax assets:
Valuation allowance	(134.8)
Deferred tax liabilities:
Valuation allowance	134.8
Net operating loss carry-forwards	111.4
Massachusetts Deferred Tax Assets [Member]
Deferred tax assets:
Valuation allowance	(11.9)
Deferred tax liabilities:
Valuation allowance	11.9
Capital Loss Carryforward [Member]
Deferred tax assets:
Valuation allowance	(7.7)
Deferred tax liabilities:
Valuation allowance	$ 7.7