New Accounting Pronouncements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Description of Financial Statement Line Items, Prospective Transition	1700
Prepaid expenses	$ 34,452	$ 34,174	$ 36,878
Assets Held-for-sale, Not Part of Disposal Group, Current, Other		113,457	103,898
Operating Lease, Right-of-Use Asset	83,376	102,268	0
Accrued liabilities	119,841	102,640	102,976
Operating Lease, Liability, Current	24,094	27,229	0
Disposal Group, Including Discontinued Operation, Liabilities		80,756	71,195
Operating Lease, Liability, Noncurrent	60,234	75,276	0
Retained earnings	619,448	566,608	569,215	$ 508,722	$ 420,659
Accounts Receivable, after Allowance for Credit Loss, Current	423,155		418,607
Other Assets, Current	93,513		108,683
Contract with Customer, Asset, Gross, Current	$ 1,100		$ 14,757
Prepaid Expenses and Other Current Assets [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		(2,704)
Discontinued Operations, Held-for-sale [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		9,559
Operating lease right-of-use assets [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		102,268
Accrued Liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		(336)
Current operating lease liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		27,229
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		9,561
Long-term operating lease liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		75,276
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		$ (2,607)