Segment and Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Total revenues	$ 280,623	$ 254,669
United States	548,755		$ 532,714
Total long-lived assets	548,755		532,714
UNITED STATES
Total revenues	209,076	185,762
United States	472,059		452,143
Total long-lived assets	472,059		452,143
CANADA
Total revenues	19,622	19,401
IRELAND
Total revenues	17,101	17,901
All Other Countries [Member]
Total revenues	34,824	$ 31,605
United States	76,696		80,571
Total long-lived assets	$ 76,696		$ 80,571