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Accounting Policies and Related Matters (Details 2) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies and Related Matters [Line Items]
Cash disbursed for acquisitions	$ (3,190,534)	$ (574,002)
Decrease (increase) in restricted cash		0
Net cash provided from (used in) investing activities	(2,133,293)	400,418
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(28,018)	(311,909)
Cash and cash equivalents at beginning of period	243,777
Cash and cash equivalents at end of period	191,199
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 281,285	295,311	$ 309,303	$ 607,220
Accounting Standards Update 2016-18 [Member] \| As Previously Reported
Accounting Policies and Related Matters [Line Items]
Cash disbursed for acquisitions		(575,694)
Decrease (increase) in restricted cash		130,470
Net cash provided from (used in) investing activities		529,196
Increase (decrease) in cash and cash equivalents		(183,131)
Cash and cash equivalents at beginning of period		419,378
Cash and cash equivalents at end of period		$ 236,247