Significant Accounting Policies (Revenue Recognition) (Details) - USD ($)		3 Months Ended								12 Months Ended
	Jan. 01, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016	[1],[2]
Disaggregation of Revenue [Line Items]
Total net revenues		$ 801,870,000	$ 732,476,000	$ 742,365,000	$ 697,192,000	$ 777,857,000	$ 690,925,000	$ 693,227,000	$ 662,677,000	$ 2,973,903,000	$ 2,824,686,000	[1],[2]	$ 2,736,080,000
Current portion of deferred revenues	$ 1,250,000,000	1,345,243,000				1,308,474,000				1,345,243,000	1,308,474,000
Long-term portion of deferred revenues	512,800,000	$ 489,329,000				$ 555,769,000				489,329,000	$ 555,769,000
Deferred revenue recognized	$ 1,250,000,000
Asset impairment charges related to contract assets										0
Products and services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total net revenues										821,111,000
Products and services transferred over time
Disaggregation of Revenue [Line Items]
Total net revenues										$ 2,152,792,000

[1] As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of therevenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenuerecognition standard.

[2] Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.