Segment Reporting - Reconciliation of Net Income to Adjusted Segment Earnings before Interest, Taxes, Depreciation and Amortization (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting [Abstract]
Net income	$ 64,598	$ 62,645	$ 43,609	$ 38,945	$ 127,243	$ 82,554
Add back:
Income tax provision	21,313		14,113		41,243	29,383
Interest income and other	(2,609)		(2,474)		(2,768)	(674)
Interest expense	4,793		6,583		9,539	12,827
Unallocated corporate expenses	28,892		25,882		50,995	49,770
Segment depreciation expense	6,556		7,574		12,920	14,438
Amortization of intangible assets	1,852		2,052		3,713	4,322
Total Adjusted Segment EBITDA	$ 125,395		$ 97,339		$ 242,885	$ 192,620