Summary of Significant Accounting Policies Cash Flow Accounting Guidance Recast (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ 452,266	$ 389,483
Capital expenditures	(165,943)	(141,652)
Acquisitions, net of cash acquired	(187,616)	(75,818)
Proceeds from divestitures and sales of property and equipment	29,890	32,588
Payments for Company-owned life insurance policies	(14,283)	(6,189)
Proceeds from Company-owned life insurance policies	2,810	2,591
Payments for (Proceeds from) Other Investing Activities	(14,525)	175
Net cash used in investing activities	(346,767)	(188,305)
Net Cash Provided by (Used in) Financing Activities	(279,051)	(147,532)
Effect of foreign currency on cash, cash equivalents, and restricted cash	(1,111)	9,463
Net (decrease) increase in cash, cash equivalents, and restricted cash		63,109
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	165,938		$ 340,601	$ 274,615	$ 211,506
Cash and cash equivalents	$ 158,301		$ 330,039	274,615
Adjustments for New Accounting Pronouncement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities		(131)
Capital expenditures		0
Acquisitions, net of cash acquired		(26,183)
Proceeds from divestitures and sales of property and equipment		20,041
Payments for Company-owned life insurance policies		(6,189)
Proceeds from Company-owned life insurance policies		2,591
Payments for (Proceeds from) Other Investing Activities		0
Net cash used in investing activities		(9,740)
Net Cash Provided by (Used in) Financing Activities		0
Effect of foreign currency on cash, cash equivalents, and restricted cash		10
Net (decrease) increase in cash, cash equivalents, and restricted cash		(9,861)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents					16,520
Cash and cash equivalents				6,659
Previous Accounting Guidance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities		389,614
Capital expenditures		(141,652)
Acquisitions, net of cash acquired		(49,635)
Proceeds from divestitures and sales of property and equipment		12,547
Payments for Company-owned life insurance policies		0
Proceeds from Company-owned life insurance policies		0
Payments for (Proceeds from) Other Investing Activities		175
Net cash used in investing activities		(178,565)
Net Cash Provided by (Used in) Financing Activities		(147,532)
Effect of foreign currency on cash, cash equivalents, and restricted cash		9,453
Net (decrease) increase in cash, cash equivalents, and restricted cash		$ 72,970
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents					$ 194,986
Cash and cash equivalents				$ 267,956