Business Combinations - Unaudited Pro Forma Results (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Business Combinations [Abstract]
Total revenues	$ 619,359	$ 547,196	$ 1,853,193	$ 1,578,627
Income before income taxes	152,038	147,351	438,289	385,327
Net income	$ 115,658	$ 109,663	$ 332,940	$ 288,373
Net income per share:
Basic (in dollars per share)	$ 0.41	$ 0.39	$ 1.18	$ 1.04
Diluted (in dollars per share)	$ 0.41	$ 0.39	$ 1.17	$ 1.02
Weighted average number of shares outstanding:
Weighted Average Basic Shares Outstanding, Pro Forma	272,962	271,008	272,425	270,423
Pro Forma Weighted Average Shares Outstanding, Diluted	275,075	275,282	274,529	275,614