Supplemental Selected Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Selected Quarterly Financial Information [Abstract]
Total revenues	$ 309,822	$ 328,334	$ 323,961	$ 303,247	$ 303,304	$ 311,350	$ 303,746	$ 281,901	$ 1,265,364	$ 1,200,301	$ 1,054,821
Gross profit	110,128	120,144	113,631	107,374	107,743	112,316	103,204	94,101	451,277	417,364	350,773
Net income	24,959	27,478	20,114	15,359	14,823	21,644	14,740	14,774	87,910	65,981	35,194
Net income attributable to controlling interests and available to common shareholders	$ 24,969	$ 27,490	$ 20,148	$ 15,384	$ 14,841	$ 22,009	$ 14,997	$ 15,233	$ 87,991	$ 67,080	$ 37,140
Net income per common share - basic	$ 0.55	$ 0.61	$ 0.45	$ 0.34	$ 0.33	$ 0.49	$ 0.33	$ 0.34	$ 1.95	$ 1.50	$ 0.83
Net income per common share - diluted	$ 0.54	$ 0.60	$ 0.44	$ 0.34	$ 0.33	$ 0.48	$ 0.33	$ 0.34	$ 1.92	$ 1.48	$ 0.82
Depreciation, accretion, and amortization of intangible assets	$ 25,100	$ 27,100	$ 27,900	$ 27,400	$ 25,700	$ 27,200	$ 25,700	$ 24,900	$ 107,524	$ 103,494	$ 99,479