Share-based Compensation (Tables)
 12 Months Ended
Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
The weighted average grant date assumptions used in calculating the fair value of options granted
The weighted average grant date assumptions used in calculating the fair value of Predecessor options granted in fiscal 2016 (Predecessor) were as follows:
 
 
Fiscal year ended September 30, 2016 (Predecessor)
Exercise price
 
$
1.83

Expected volatility(1)
 
83.09
%
Expected life (in years)(2) 
 
5.00

Risk-free interest rate(3)
 
1.53
%
Dividend yield(4)
 
—
%
(1) Expected volatility based on a combination of the Company's historical volatility and peer group companies' implied volatility.
(2) Expected life based on the vesting terms of the option and a contractual life of ten years.
(3) Risk-free interest rate based on U.S. Treasury spot rate for the expected term of the option.
(4) Dividend yield was assumed to be zero as the Company did not pay dividends.
The weighted average grant date assumptions used in calculating the fair value of Successor options granted on the Emergence Date and thereafter were as follows:
 
Period from December 16, 2017
through
September 30, 2018
 
Emergence Date Grants
Exercise price
$
21.66

 
$
19.46

Expected volatility(1)
49.67
%
 
56.59
%
Expected life (in years)(2) 
5.86

 
6.65

Risk-free interest rate(3)
2.72
%
 
2.35
%
Dividend yield(4)
—
%
 
—
%
(1) Expected volatility based on peer group companies adjusted for the Company's leverage.
(2) Expected life based on the vesting terms of the option and a contractual life of ten years.
(3) Risk-free interest rate based on U.S. Treasury yields with a term equal to the expected option term.
(4) Dividend yield was assumed to be zero as the Company does not anticipate paying dividends.
A summary of option activity
A summary of option activity under the 2017 Equity Incentive Plan for the period from the Emergence Date through September 30, 2018 (Successor) is presented below:
 
 
Options (In thousands)
 
Weighted Average Exercise Price
 
Weighted Average Remaining Contractual Term (in years)
 
Aggregate Intrinsic Value (In thousands)
Granted
 
1,255

 
$
19.65

 
 
 
 
Exercised
 
(3
)
 
$
19.46

 
 
 
 
Forfeited or expired
 
(134
)
 
$
19.71

 
 
 
 
Outstanding at September 30, 2018 (Successor)
 
1,118

 
$
19.64

 
8.9
 
$
2,794

 
 
 
 
 
 
 
 
 
Exercisable at September 30, 2018 (Successor)
 
106

 
$
19.69

 
5.6
 
$
260
A summary of RSU activity
A summary of RSU activity under the 2017 Equity Incentive Plan from the Emergence Date through September 30, 2018 (Successor) is presented below:
 
 
Restricted Stock Units (In thousands)
Granted
 
4,048

Vested
 
(379
)
Forfeited
 
(427
)
Non-vested at September 30, 2018 (Successor)
 
3,243