Incentive Plans - Additional Information about Stock Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options Outstanding, No. of Options (in shares) | shares	2,048,400
Options Outstanding, Avg. Life Remaining in Years	1 year 7 months 6 days
Options Outstanding, Aggregate Intrinsic Value | $	$ 0
Options Exercisable, No. of Options (in shares) | shares	2,048,400
Options Exercisable, Avg. Life Remaining in Years	1 year 7 months 6 days
Options Exercisable, Aggregate Intrinsic Value | $	$ 0
$17.00 to $30.99
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of exercise prices per option, lower limit (in USD per share) | $ / shares	$ 17.00
Range of exercise prices per option, upper limit (in USD per share) | $ / shares	$ 30.99
Options Outstanding, No. of Options (in shares) | shares	984,500
Options Outstanding, Avg. Life Remaining in Years	2 years 6 months
Options Outstanding, Aggregate Intrinsic Value | $	$ 0
Options Exercisable, No. of Options (in shares) | shares	984,500
Options Exercisable, Avg. Life Remaining in Years	2 years 6 months
Options Exercisable, Aggregate Intrinsic Value | $	$ 0
$31.00 to $50.99
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of exercise prices per option, lower limit (in USD per share) | $ / shares	$ 31.00
Range of exercise prices per option, upper limit (in USD per share) | $ / shares	$ 50.99
Options Outstanding, No. of Options (in shares) | shares	655,000
Options Outstanding, Avg. Life Remaining in Years	1 year 1 month 6 days
Options Outstanding, Aggregate Intrinsic Value | $	$ 0
Options Exercisable, No. of Options (in shares) | shares	655,000
Options Exercisable, Avg. Life Remaining in Years	1 year 1 month 6 days
Options Exercisable, Aggregate Intrinsic Value | $	$ 0
$51.00 to $65.00
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of exercise prices per option, lower limit (in USD per share) | $ / shares	$ 51.00
Range of exercise prices per option, upper limit (in USD per share) | $ / shares	$ 65.00
Options Outstanding, No. of Options (in shares) | shares	408,900
Options Outstanding, Avg. Life Remaining in Years	1 month 6 days
Options Outstanding, Aggregate Intrinsic Value | $	$ 0
Options Exercisable, No. of Options (in shares) | shares	408,900
Options Exercisable, Avg. Life Remaining in Years	1 month 6 days
Options Exercisable, Aggregate Intrinsic Value | $	$ 0