Segment Information (Geographic Information of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 245,346	$ 227,401	$ 814,054	$ 679,441
Operating Segments [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	245,346	227,401	814,054	679,441
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	114,410	107,812	392,904	327,838
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	52,711	51,136	201,296	170,994
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	43,935	29,065	123,335	81,930
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 34,290	$ 39,388	$ 96,519	$ 98,679