Stock-Based Compensation - Summary of Status of Plans (Details)	12 Months Ended
	Dec. 31, 2020 shares
2018 Plan
Summary of Status of Equity-Based Compensation Plans
Awards originally available to be granted	2,500,000
Maximum potential awards outstanding	503,481
RSUs and cash settled awards vested and released	45,539
Awards available to be granted	1,950,980
2018 Plan | RSUs
Summary of Status of Equity-Based Compensation Plans
Shares outstanding	503,481
2014 Plan
Summary of Status of Equity-Based Compensation Plans
Awards originally available to be granted	1,500,000
Maximum potential awards outstanding	178,900
2014 Plan | RSUs
Summary of Status of Equity-Based Compensation Plans
Shares outstanding	178,900
2009 Plan
Summary of Status of Equity-Based Compensation Plans
Awards originally available to be granted	3,400,000
Maximum potential awards outstanding	92,600
2009 Plan | RSUs
Summary of Status of Equity-Based Compensation Plans
Shares outstanding	92,600
2004 Plan
Summary of Status of Equity-Based Compensation Plans
Awards originally available to be granted	6,500,000
Maximum potential awards outstanding	35,952
2004 Plan | RSUs
Summary of Status of Equity-Based Compensation Plans
Shares outstanding	35,952
Directors' Plan
Summary of Status of Equity-Based Compensation Plans
Maximum potential awards outstanding	5,522
Directors' Plan | RSUs
Summary of Status of Equity-Based Compensation Plans
Shares outstanding	5,522