Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Schedule of Common Stock Activity

The following table summarizes Common Stock activity during the periods presented below:

	Year Ended December 31,
	2020	2019	2018
	(In millions)
Shares outstanding at the beginning of the period	96.9	110.4	105.2
Shares issued for preferred share conversions	—	—	25.5
Shares issued for vested restricted stock units	1.3	1.5	1.1
Shares issued for disputed claims	—	—	0.1
Shares repurchased	(0.4)	(15.0)	(21.5)
Shares outstanding at the end of the period	97.8	96.9	110.4

Summary of Preferred Stock Activity

The following table summarizes the Series A Convertible Preferred Stock activity during the periods presented below:

	Year Ended December 31, 2018
Shares outstanding at the beginning of the period	13.5
Shares converted to Common Stock	(13.5)
Shares outstanding at the end of the period	—