Note 13. Common Stock and Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Stock Options Roll Forward

	Number of Shares	Weighted Average Grant-Date Fair Value per Award		Weighted Average Remaining Contractual Terms (Years)	Aggregate Intrinsic Value (in millions)
Options outstanding at December 31, 2019	—	$	—
Granted	300,000	$	5.26
Exercised	—	$	—
Cancelled	—	$	—
Options outstanding at December 31, 2020	300,000	$	5.26	9.1	$	1.4

Share-based Payment Arrangement, Option, Exercise Price Range

The fair value of the stock options granted was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:

	Year Ended December 31, 2020
Exercise price	$	21.61
Risk-free interest rate	1.48		%
Expected life (in years)	6.50
Equity volatility	35.00		%
Dividend yield	3.42		%

Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block]

	Number of Restricted Share Awards	Weighted Average Grant-Date Fair Value per Award
Restricted share awards outstanding at December 31, 2019	5,055,461	$	20.99
Granted	1,022,115	$	18.62
Vested	(1,802,836)	$	21.70
Forfeited	(476,309)	$	20.59
Restricted share awards outstanding at December 31, 2020 (1)	3,798,431	$	20.06

(1) The balance of restricted share awards outstanding at December 31, 2020 includes approximately 0.7 million restricted shares for Arcosa employees that were converted under the shareholder method at the time of the Arcosa spin-off. These restricted shares will be released to Arcosa employees upon vesting, but as of the spin-off date, Trinity no longer records the compensation expense associated with these shares

Share-based Payment Arrangement, Performance Shares, Activity [Table Text Block]

	Number of Performance Units	Weighted Average Grant-Date Fair Value per Award
Performance units outstanding at December 31, 2019	800,762	$	26.33
Granted	444,252	$	20.31
Vested	(3,091)	$	28.35
Forfeited	(6,751)	$	24.74
Performance units outstanding at December 31, 2020	1,235,172	$	24.17

Schedule of Repurchase Agreements

Share repurchase activity under this program was as follows:

	Shares Repurchased			Remaining Authorization to Repurchase
Period	Number of shares	Cost (in millions)		Cost (in millions)
March 7, 2019 Authorization				$	350.0
March 7, 2019 through March 31, 2019	866,715	$	19.0	$	331.0
April 1, 2019 through June 30, 2019	2,133,116	44.0		$	287.0
July 1, 2019 through September 30, 2019	5,171,489	100.9		$	186.1
October 1, 2019 through December 31, 2019	2,933,474	60.8		$	125.3
January 1, 2020 through March 31, 2020	1,850,000	35.4		$	89.9
April 1, 2020 through June 30, 2020	—	—		$	89.9
July 1, 2020 through September 30, 2020	4,466,896	89.9		$	—
Total	17,421,690	$	350.0

Share repurchase activity under this program is as follows:

	Shares Repurchased			Remaining Authorization to Repurchase
Period	Number of shares	Cost (in millions)		Cost (in millions)
October 23, 2020 Authorization				$	250.0
October 23, 2020 through December 31, 2020	2,974,922	$	67.8	$	182.2
Total	2,974,922	$	67.8