Industry Segment and Geographic Information Revenues from External Customers and Long-lived Assets by Geographic Areas (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 309,687	$ 302,534	$ 297,584	$ 279,541	$ 273,803	$ 261,531	$ 259,875	$ 253,573	$ 1,189,346	$ 1,048,782	$ 1,002,286
Long-Lived Assets	941,546				965,102				$ 941,546	$ 965,102
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Customer Representation Of Revenue, Percentage									72.00%	79.00%	85.00%
Total revenues									$ 855,255	$ 825,721	$ 851,413
Long-Lived Assets	640,277				596,820				640,277	596,820
CANADA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									26,696	27,267	30,252
UNITED KINGDOM
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									66,723	49,430	28,309
Long-Lived Assets	299,660				366,594				299,660	366,594
Non-US [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									240,672	146,364	$ 92,312
ISRAEL
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	$ 1,609				$ 1,688				$ 1,609	$ 1,688