Shareholders' Equity - Common Stock and Debt Repurchase Authorizations (Details) - USD ($)	3 Months Ended				12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2020	Nov. 07, 2019	Jul. 26, 2019	Nov. 02, 2018
Class of Stock [Line Items]
Dividends declared or paid	$ 0	$ 0	$ 0	$ 0
Repurchase Program, November 2018
Class of Stock [Line Items]
Debt repurchase program, amount authorized								$ 100,000,000
Remaining authorized repurchase amount under debt repurchase	$ 76,000,000				$ 76,000,000
Common Stock | Repurchase Progam, November 2019
Class of Stock [Line Items]
Authorized repurchase of securities, with debt reduction target (up to)						$ 325,000,000	$ 250,000,000
Number of shares authorized to be repurchased (in shares)	0	0			11,800,000
Shares repurchased during period					$ 266,000,000
Remaining authorized repurchase amount under the stock repurchase program	$ 59,000,000
Common Stock | Repurchase Program, November 2018
Class of Stock [Line Items]
Authorized repurchase of securities, with debt reduction target (up to)								$ 200,000,000