Selected Quarterly Financial Data (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
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 2,477,541	$ 2,290,188	$ 2,105,204	$ 1,957,736	$ 1,823,333	$ 1,738,355	$ 1,644,694	$ 1,573,129	$ 8,830,669	$ 6,779,511	$ 5,504,656
Gross profit	823,122	757,344	632,106	588,196	573,968	564,397	522,942	526,728
Net income	$ 66,748	$ 51,517	$ 40,755	$ 27,658	$ 43,178	$ 29,432	$ 26,335	$ 23,696	$ 186,678	$ 122,641	$ 266,799
Earnings (loss) per share:
Basic (in USD per share)	$ 0.16	$ 0.12	$ 0.10	$ 0.06	$ 0.10	$ 0.07	$ 0.06	$ 0.06	$ 0.44	$ 0.29	$ 0.63
Diluted (in USD per share)	$ 0.15	$ 0.12	$ 0.09	$ 0.06	$ 0.10	$ 0.07	$ 0.06	$ 0.05	$ 0.43	$ 0.28	$ 0.62