Supplemental Cash Flow Information (Tables)

12 Months Ended

Dec. 31, 2017

Supplemental Cash Flow Elements [Abstract]

Supplemental Cash Flow Information

The table below provides supplemental cash flow information:

	Year ended December 31,
	2017		2016		2015
Cash paid:
Income taxes	$	387,159	$	339,411	$	156,075
Interest	424,547		406,987		405,120
Non-cash investing and financing activities:
Fixed assets under capital lease obligations	48,378		28,127		74,035