Stock-Based Compensation (Tables)

3 Months Ended

12 Months Ended

Dec. 31, 2021

Dec. 31, 2021

Share-based Payment Arrangement, Noncash Expense [Abstract]

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block]

A summary of stock-based compensation costs is as follows (in millions):

	Year Ended December 31,
	2021		2020
Notional stock units and stock appreciation rights	$	11.6	$	6.6
Restricted stock units	0.5		0.4
Stock options	0.1		0.1
Total stock-based compensation costs	$	12.2	$	7.1
Total recognized tax benefit	$	(1.5)	$	—

Share-based Payment Arrangement, Nonemployee Director Award Plan, Activity [Table Text Block]

The following table summarizes Centrus’ board restricted stock units activity:

	Shares (in thousands)	Weighted Average Grant Date Fair Value (per share)
Nonvested at December 31, 2019	74	$3.09
Granted	47	$10.38
Vested	(74)	$3.09
Forfeited	—	—
Nonvested at December 31, 2020	47	$10.38
Granted	20	$25.13
Vested	(47)	$10.38
Forfeited	—	—
Nonvested at December 31, 2021	20	$25.13

Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]

The following table summarizes Centrus’s employee restricted stock units activity:

	Shares (in thousands)	Weighted Average Grant Date Fair Value (per share)
Nonvested at December 31, 2020	—	$—
Granted	4	$24.01
Vested	—	—
Forfeited	—	—
Nonvested at December 31, 2021	4	$24.01

Share-based Compensation, Stock Options, Activity [Table Text Block]

A summary of stock option activity follows:

	Stock Options (in thousands)	Weighted Average Exercise Price	Weighted Average Remaining Contractual Life in Years	Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2019	518	$4.02	6.2	$1.5
Granted	—	—	—	—
Exercised	(107)	$3.43	—	—
Forfeited/Cancelled	—	—	—	—
Outstanding at December 31, 2020	411	$4.18	5.3	$7.8
Granted	—	—	—	—
Exercised	(217)	$4.17	—	—
Forfeited/Cancelled	—	—	—	—
Outstanding at December 31, 2021	194	$4.18	4.4	$8.9
Exercisable at December 31, 2021	144	$4.37	3.2	$6.6

Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding and Exercisable [Table Text Block]

Stock options outstanding and options exercisable at December 31, 2021, are as follows:

Stock Exercise Price	Options Outstanding (thousands)	Remaining Contractual Life in Years	Options Exercisable (thousands)
$4.37	144	3.2	144
$3.65	50	7.8	—

Share-based Payment Arrangement, Stock Appreciation Right, Activity [Table Text Block]

A summary of SARs with time-based vesting granted under the 2014 plan for the year ended December 31, 2021, are as follows:

	Stock Appreciation Rights (in thousands)	Weighted Average Exercise Price	Weighted Average Remaining Contractual Life in Years	Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2019	—	$—	—	$—
Granted	83.5	$5.53	—	—
Exercised	—	—	—	—
Forfeited/Cancelled	—	—	—	—
Outstanding at December 31, 2020	83.5	$5.53	2.3	$1.47
Granted	—	—	—	—
Exercised	—	—	—	—
Forfeited/Cancelled	—	—	—	—
Outstanding at December 31, 2021	83.5	$5.53	1.3	$3.71
Exercisable at December 31, 2021	83.5	$5.53	1.3	$3.71

Schedule of Share-based Payment Award, Stock Appreciation Rights, Valuation Assumptions [Table Text Block]

The weighted-average assumptions used in the valuation models to determine the fair value of SARs granted to employees under the 2014 Plan are as follows:

	Year Ended December 31,
	2021	2020
SARs Granted (in thousands)	n/a	83.5
Average Risk-Free Rate	n/a	0.14%
Expected Volatility	n/a	94%
Expected Term (Years)	n/a	2.3
Dividend Yield	n/a	—

Share-based Payment Arrangement, Stock Appreciation Right, Performance Condition, Activity [Table Text Block]

A summary of SARs with performance-based vesting granted under the 2014 plan in the year ended December 31, 2021, are as follows:

	Stock Appreciation Rights (Performance Condition) (in thousands)	Weighted Average Exercise Price	Weighted Average Remaining Contractual Life in Years	Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2020	—	$—	—	$—
Granted	21	$19.44	—	—
Exercised	—	—	—	—
Forfeited/Cancelled	—	—	—	—
Outstanding at December 31, 2021	21	$19.44	2.3	$0.64
Exercisable at December 31, 2021	21	$19.44	2.3	$0.64

Schedule of Share-based Payment Award, Stock Appreciation Rights, Performance Condition, Valuation Assumptions [Table Text Block]

The weighted-average assumptions used in the valuation models to determine the fair value of SARs granted to employees under the 2014 Plan are as follows:

	Year Ended December 31,
	2021	2020
Stock Appreciation Rights Granted (in thousands)	21.0	n/a
Average Risk-Free Rate	0.3%	n/a
Expected Volatility	82.8%	n/a
Expected Term (Years)	2.5	n/a
Dividend Yield	—	n/a

Schedule of Notional Stock Units, Activity [Table Text Block]

A summary of notional stock units with time-based vesting granted under the 2014 plan for the year ended December 31, 2021, are as follows:

	Shares (thousands)	Weighted Average Grant Date Fair Value (per share)
Nonvested at December 31, 2019	468	$3.16
Granted	125	$5.53
Vested	—	—
Forfeited	(22)	$3.16
Nonvested at December 31, 2020	571	$3.68
Granted	—	—
Vested	(319)	$3.16
Forfeited	—	—
Nonvested at December 31, 2021	252	$4.33

Schedule of Notional Stock Units, Performance Condition, Activity [Table Text Block]

A summary of notional stock units with performance-based vesting granted under the 2014 plan for the year ended December 31, 2021, are as follows:

	Shares (in thousands)	Weighted Average Grant Date Fair Value (per share)
Nonvested at December 31, 2020	—	$	—
Granted	10	$39.55
Vested	—	—
Forfeited	—	—
Nonvested at December 31, 2021	10	$39.55