Acquisitions - Business Acquisition Pro Forma Information (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) $ / shares
Business Combinations [Abstract]
Net sales	$ 434,526
Income before income taxes	81,924
Net income	$ 63,933
Net income per share — basic (in dollars per share) | $ / shares	$ 2.57
Net income per share — diluted (in dollars per share) | $ / shares	$ 2.53