Significant Accounting Policies (Changes in Goodwill) (Details)	3 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) reporting_unit		Dec. 31, 2017 USD ($) reporting_unit
Goodwill [Line Items]
Amortization of intangible assets					$ 18,000,000
Goodwill and intangible asset impairment	$ 0	$ 0
Number of goodwill reporting units | reporting_unit			1		2
Goodwill [Roll Forward]
Beginning balance			$ 1,614,494,000		$ 1,585,893,000
Additions			188,176,000	[1]	28,601,000	[2]
Other			0		0
Ending balance		$ 1,614,494,000	$ 1,802,670,000		1,614,494,000
Impairment of Product-related Intangible Assets
Goodwill [Line Items]
Amortization of intangible assets					15,500,000
Impairment of Other Intangible Assets
Goodwill [Line Items]
Amortization of intangible assets					$ 2,500,000

[1] Amount relates to preliminary purchase price allocation of goodwill associated with the 2018 business combinations. See Note 4 for more information regarding the Company's acquisitions.

[2] Amount relates to the purchase price allocation of goodwill associated with the 2017 business combination. See Note 4 for more information regarding the Company's acquisitions.