Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Compensation Expense Related To Stock-Based Compensation

Stock-based compensation expense, net of forfeitures, which is included in "Salaries, wages, and benefits" in the consolidated income statements is comprised of the following:



	2017		2016		2015
	(In thousands)
Stock options	$	1,788	$	1,734	$	1,061
Restricted stock units and restricted stock awards	4,004		1,506		4,038
Performance units	450		801		1,913
Stock-based compensation expense – equity awards	$	6,242	$	4,041	$	7,012
Stock-based compensation expense – liability awards ⁽¹⁾	148		—		—
Total stock-based compensation expense, net of forfeitures	6,390		4,041		7,012
Income tax benefit	$	2,415	$	1,515	$	2,630

____________


(1)	Includes awards granted to executive management in November 2017 that ultimately settle in cash upon fulfilling a requisite service period (for restricted stock units) and fulfilling a requisite service period and achieving performance targets (for performance units).

Schedule of Unrecognized Compensation Cost, Nonvested Awards [Table Text Block]

The following table presents the total unrecognized stock-based compensation expense and the expected weighted average period over which these expenses will be recognized:



	December 31, 2017
	Expense		Weighted Average Period
	(In thousands)		(In years)
Equity awards – Stock options	$	3,878	1.8
Equity awards – Restricted stock units and restricted stock awards	19,156		2.3
Equity awards – Performance units	1,303		3.1
Liability awards – Restricted stock units and performance units	3,169		2.7
Total unrecognized stock-based compensation expense	$	27,506	2.3

Summary Of Activity Related To Stock Options

A summary of 2017 stock option activity follows:



Stock options outstanding:	Shares Under Option		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value ⁽¹⁾
					(In years)	(In thousands)
Stock options outstanding at December 31, 2016	1,737,400		$	23.19	2.9	$	17,200
Granted	497,421		33.35
Assumed Swift stock options from 2017 Merger	528,466		21.93
Exercised	(589,020	)	21.44
Expired	(24,552	)	24.44
Forfeited	(190,424	)	27.96
Stock options outstanding at December 31, 2017	1,959,291		$	25.48	3.2	$	35,779
Aggregate number of stock options expected to vest at a future date as of December 31, 2017	969,965		29.00		3.5	$	14,283
Exercisable at December 31, 2017	918,594		$	21.29	2.8	$	20,428

____________


(1)	The aggregate intrinsic value was computed using the closing share price on December 29, 2017 of $43.72 and on December 30, 2016 of $32.83, as applicable.

Weighted Average Assumptions

The following table presents the weighted average assumptions used in the fair value computation:



Stock option fair value assumptions:	2017	2016	2015
Dividend yield ⁽¹⁾	0.72%	0.99%	0.8%
Risk-free rate of return ⁽²⁾	1.49%	0.90%	0.98%
Expected volatility ⁽³⁾	27.95%	27.91%	25.88%
Expected term (in years) ⁽⁴⁾	3.2	2.7	2.7
Weighted average fair value of stock options granted	$6.78	$4.28	$5.00

____________


(1)	The dividend yield assumption is based on Knight's historical experience and anticipated future dividend payouts.


(2)	The risk-free interest rate assumption is based on the United States Treasury securities at a constant maturity with a maturity period that most closely resembles the expected term of the stock option award.


(3)	Expected volatility of the Company's Class A common stock is determined based on Knight's historical data.


(4)	The expected term of employee stock options represents the weighted-average period the stock options are expected to remain outstanding and was determined based on an analysis of historical exercise behavior.

Summary Of Exercise Of Stock Options

The following table summarizes stock option exercise information for the years presented:



Stock option exercises	2017		2016		2015
	(In thousands, except share data)
Number of stock options exercised	589,020		708,244		594,673
Intrinsic value of stock options exercised	$	8,792	$	7,100	$	8,300
Cash received upon exercise of stock options	$	13,159	$	13,188	$	9,930
Income tax benefit	$	1,833	$	1,847	$	3,175

Rollforward of Company's Nonvested Stock Options

The following table is a rollforward of the Company's unvested stock options:



Unvested stock options:	Shares		Weighted Average Fair Value
Unvested stock options at December 31, 2016	1,131,773		$	4.39
Granted	497,421		6.78
Vested	(398,073	)	4.18
Forfeited	(190,424	)	5.10
Unvested stock options at December 31, 2017	1,040,697		$	5.49

Schedule of Grants of Restricted Stock [Table Text Block]

Stock Award Grants



	2017	2016	2015
Stock options	497,421	569,480	590,141
Restricted stock units and restricted stock awards	266,958	17,000	13,950
Performance units	44,244	177,741	165,720
Equity awards granted	808,623	764,221	769,811
Liability awards granted⁽¹⁾	77,620	—	—
Total stock awards granted	886,243	764,221	769,811

____________


(1)	Includes 46,572 performance units and 31,048 restricted stock units

Rollforward of Nonvested Restricted Stock Awards [Table Text Block]

The following table is a rollforward of unvested restricted stock units, including restricted stock units classified as equity and those classified as liabilities:



Unvested restricted stock units:	Number of Awards		Weighted Average Fair Value ⁽¹⁾
Unvested restricted stock units at December 31, 2016	686,786		$	16.46
Granted	298,006		36.44
Assumed Swift restricted stock units from 2017 Merger	168,488		40.85
Vested	(126,871	)	16.77
Forfeited	(46,692	)	23.59
Unvested restricted stock units at December 31, 2017	979,717		$	26.59

____________


(1)	The fair value of each restricted stock unit is based on the closing market price on the grant date, except for the Swift restricted stock unit awards assumed, which were re-measured at the Merger Date.

Rollforward of Nonvested Performance Shares [Table Text Block]

The following table is a rollforward of unvested performance units, including performance units classified as equity and those classified as liabilities:



Unvested performance units:	Shares		Weighted Average Fair Value
Unvested performance units at December 31, 2016	508,478		$	25.60
Granted ⁽¹⁾	90,816		$	40.81
Assumed Swift performance units from 2017 Merger	56,817		$	40.85
Shares earned above target	21,117		$	23.85
Vested	(519,483	)	$	25.53
Forfeited	(10,112	)	$	25.40
Unvested performance units at December 31, 2017	147,633		$	35.34

____________


(1)	The performance measurement period for performance units granted in 2017 is January 1, 2018 to December 31, 2020 (three full calendar years). These awards will vest one month following the expiration of the performance measurement period

Performance unit fair value assumptions

The following table presents the weighted average assumptions used in the fair value computation for performance units, including performance units classified as equity and those classified as liabilities:



Performance unit fair value assumptions:	2017			2016			2015
Dividend yield⁽¹⁾	0.59		%	0.99		%	0.80		%
Expected volatility⁽²⁾	31.28		%	27.95		%	23.18		%
Average peer volatility⁽²⁾	28.45		%	34.37		%	30.70		%
Average peer correlation coefficient⁽³⁾	0.60			0.60			0.49
Risk-free interest rate⁽⁴⁾	1.88		%	0.89		%	0.78		%
Expected term (in years)⁽⁵⁾	3.1			2.8			2.6
Weighted-average fair value of performance units granted	$	40.81		$	23.89		$	29.30

____________


(1)	The dividend yield, used to project stock price to the end of the performance period, is based on the Knight's historical experience and future expectation of dividend payouts. Total stockholder return is determined assuming that dividends are reinvested in the issuing entity over the performance period, which is mathematically equivalent to utilizing a 0% dividend yield.


(2)	Management (or peer company) estimated volatility using Knight's (or peer company's) historical share price performance over the remaining performance period as of the grant date.


(3)	The correlation coefficients are used to model the way in which each entity tends to move in relation to each other; the correlation assumptions were developed using the same stock price data as the volatility assumptions.


(4)	The risk-free interest rate assumption is based on United States Treasury securities at a constant maturity with a maturity period that most closely resembles the expected term of the performance award.


(5)	Since the Monte Carlo Simulation valuation is an open form model that uses an expected life commensurate with the performance period, the expected life of the performance units was assumed to be the period from the grant date to the end of the performance period.