Business Combinations Purchase Price Allocation (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Jan. 05, 2018
Business Acquisition [Line Items]
Business Combination, Current Assets				$ 86,962
Business Combination, Property, Plant, and Equipment				27,670
Business Combination, Other Noncurrent Assets	[1]			(830)
Business Combination, Intangibles Assets				226,200
Acquired Intangible Assets, Weighted Average Useful Life		8 years
Business Combination, Intangible Assets, Other than Goodwill				240,600
Goodwill acquired		$ 572,499
Business Combination, Current Liabilities				(91,857)
Finite-Lived Intangible Liabilities Acquired		(23,900)	$ 0
Business Combination, Noncurrent Liabilities				1,928
SIlver Spring Networks, Inc. [Member]
Business Acquisition [Line Items]
Goodwill acquired		572,500
Business Combination, Goodwill, and Liabilities Assumed, Net				809,216
Business Acquisition, Transaction Costs		$ 15,600
Core Developed Technology [Member]
Business Acquisition [Line Items]
Business Combination, Intangibles Assets				81,900
Acquired Intangible Assets, Weighted Average Useful Life		5 years
Customer Contracts And Relationships [Member]
Business Acquisition [Line Items]
Business Combination, Intangibles Assets				133,500
Acquired Intangible Assets, Weighted Average Useful Life		10 years
Finite-Lived Intangible Liabilities Acquired		$ (23,900)
Acquired Finite-lived Intangible Liabilities, Weighted Average Useful Life		5 years
Trademarks and Trade Names [Member]
Business Acquisition [Line Items]
Business Combination, Intangibles Assets				10,800
Acquired Intangible Assets, Weighted Average Useful Life		3 years
In Process Research and Development [Member]
Business Acquisition [Line Items]
Business Combination, Intangibles Assets				$ 14,400

[1] Reflects adjustments to deferred tax assets and liabilities, net as a result of the acquisition, and is classified as part of our overall consolidated deferred tax asset. This negative deferred tax asset more than offsets the fair value of other noncurrent assets acquired.