Revenue Recognition (Change to Prior Revenue Guidance Related to Classification in The Statements of Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Service revenue and sales	$ 1,938,555	$ 1,782,648	$ 1,666,724
Cost of services provided and goods sold	1,321,126	1,227,644	1,150,532
Selling, general and administrative expenses	$ 305,712	271,209	$ 276,652
ASC 605 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Service revenue and sales		1,811,408
Cost of services provided and goods sold		1,238,698
Selling, general and administrative expenses		288,915
Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Service revenue and sales		(28,760)
Cost of services provided and goods sold		(10,054)
Selling, general and administrative expenses		(18,706)
ASC 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Service revenue and sales		1,782,648
Cost of services provided and goods sold		1,228,644
Selling, general and administrative expenses		$ 270,209