Segment Reporting - Reconciliation of Net Income to Adjusted Segment Earnings before Interest, Taxes, Depreciation and Amortization (Details) - USD ($)	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting [Abstract]
Net income	$ 50,172,000	$ 48,174,000	$ 56,747,000	$ 60,422,000	$ 64,598,000	$ 62,645,000	$ 155,093,000	$ 187,665,000
Add back:
Income tax provision	14,407,000			19,857,000			45,342,000	61,100,000
Interest income and other	3,340,000			(2,973,000)			(3,879,000)	(5,741,000)
Interest expense	5,151,000			4,832,000			15,169,000	14,371,000
Unallocated corporate expenses	26,061,000			27,783,000			79,928,000	78,778,000
Segment depreciation expense	7,236,000			7,389,000			21,573,000	20,309,000
Amortization of intangible assets	2,795,000			2,125,000			7,440,000	5,838,000
Segment special charges	6,730,000			0			6,730,000	0
Total Adjusted Segment EBITDA	115,892,000			119,435,000			327,396,000	362,320,000
Segment Reporting Information [Line Items]
Restructuring Charges	7,103,000			$ 0			7,103,000	$ 0
Unallocated Corporate
Segment Reporting Information [Line Items]
Restructuring Charges	$ 373,000						$ 373,000