Summary of Significant Accounting Policies Cash Flow Accounting Guidance Recast (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 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	$ 315,376	$ 222,489
Capital expenditures	(102,890)	(85,324)
Acquisitions, net of cash acquired	(167,622)	(46,373)
Proceeds from divestitures and sales of property and equipment	18,305	25,329
Payments for Company-owned life insurance policies	(11,733)	(3,180)
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	(272,755)	(106,782)
Net Cash Provided by (Used in) Financing Activities	(210,116)	(96,626)
Effect of foreign currency on cash, cash equivalents, and restricted cash	(2,133)	4,072
Net (decrease) increase in cash, cash equivalents, and restricted cash		23,153
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	170,973		$ 340,601	$ 234,659	$ 211,506
Cash and cash equivalents	$ 164,460		$ 330,039	234,659
Adjustments for New Accounting Pronouncement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities		(1,734)
Capital expenditures		0
Acquisitions, net of cash acquired		(22,329)
Proceeds from divestitures and sales of property and equipment		17,898
Payments for Company-owned life insurance policies		(3,180)
Proceeds from Company-owned life insurance policies		2,591
Net cash used in investing activities		(5,020)
Net Cash Provided by (Used in) Financing Activities		0
Effect of foreign currency on cash, cash equivalents, and restricted cash		4
Net (decrease) increase in cash, cash equivalents, and restricted cash		(6,750)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents					16,520
Cash and cash equivalents				9,770
Previous Accounting Guidance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities		224,223
Capital expenditures		(85,324)
Acquisitions, net of cash acquired		(24,044)
Proceeds from divestitures and sales of property and equipment		7,431
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		(101,762)
Net Cash Provided by (Used in) Financing Activities		(96,626)
Effect of foreign currency on cash, cash equivalents, and restricted cash		4,068
Net (decrease) increase in cash, cash equivalents, and restricted cash		$ 29,903
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents					$ 194,986
Cash and cash equivalents				$ 224,889