Summary of Significant Accounting Polices (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Schedule of Estimated Useful Life

For financial reporting purposes, assets are generally depreciated using the following estimated useful lives and salvage values:

	Lives	Salvage Values
Building and improvements	30 years	0%
Tractors	80 months	0%
Trailers	12 years	$1,000
Service and other equipment	3-10 years	0%

Schedule Of Basic and Diluted Earnings Per Share

The computation of basic and diluted earnings per share is shown below (in thousands, except per share amounts).

	Years Ended December 31,
	2017		2016		2015
Net income	$	202,889	$	79,129	$	123,714
Weighted average common shares outstanding	72,270		72,057		71,957
Dilutive effect of stock-based awards	288		336		599
Shares used in computing diluted earnings per share	72,558		72,393		72,556
Basic earnings per share	$	2.81	$	1.10	$	1.72
Diluted earnings per share	$	2.80	$	1.09	$	1.71