Segment Information - Schedule of Fixed Assets, Goodwill and Intangibles, Net (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Long-lived Assets	$ 90,306				$ 78,377				$ 90,306	$ 78,377
Intangible Assets, Net (Including Goodwill)	906,540				929,830				906,540	929,830
Revenue	402,747	$ 375,800	$ 390,532	$ 344,700	390,442	$ 349,254	$ 337,047	$ 309,042	1,513,779	1,385,785	$ 1,326,256
United States
Segment Reporting Information [Line Items]
Long-lived Assets	77,163				67,617				77,163	67,617
Intangible Assets, Net (Including Goodwill)	706,241				736,334				706,241	736,334
Revenue									1,172,364	1,103,714	1,085,051
Canada
Segment Reporting Information [Line Items]
Long-lived Assets	5,638				5,887				5,638	5,887
Intangible Assets, Net (Including Goodwill)	127,014				121,987				127,014	121,987
Revenue									123,092	124,101	129,039
Other Geographical Location
Segment Reporting Information [Line Items]
Long-lived Assets	7,505				4,873				7,505	4,873
Intangible Assets, Net (Including Goodwill)	$ 73,285				$ 71,509				73,285	71,509
Revenue									$ 218,323	$ 157,970	$ 112,166