Stock-Based Compensation, Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares [Roll Forward]
Exercised (in shares)	(400,000)	0	(500,000)
Stock Options [Member]
Number of Shares [Roll Forward]
Outstanding at beginning of year (in shares)	3,120,900
Granted (in shares)	1,079,300
Exercised (in shares)	(230,900)
Forfeited/cancelled/expired (in shares)	(800,700)
Outstanding at end of year (in shares)	3,168,600	3,120,900
Exercisable at end of year (in shares)	1,336,300
Weighted-Average Exercise Price [Roll Forward]
Outstanding at beginning of year (in dollars per share)	$ 55.38
Granted (in dollars per share)	30.45
Exercised (in dollars per share)	31.97
Forfeited/cancelled/expired (in dollars per share)	70.55
Outstanding at end of year (in dollars per share)	44.76	$ 55.38
Exercisable at end of year (in dollars per share)	$ 43.18
Remaining Contractual Term and Aggregate Intrinsic Value [Abstract]
Outstanding options, weighted-average remaining contractual term	4 years 2 months 12 days
Outstanding options, aggregate intrinsic value	$ 45,130
Exercisable options, weighted-average remaining contractual term	2 years 5 months 23 days
Exercisable options, aggregate intrinsic value	$ 19,124
Service-Based Options [Member]
Number of Shares [Roll Forward]
Outstanding at beginning of year (in shares)	962,500
Granted (in shares)	0
Exercised (in shares)	(114,700)
Forfeited/cancelled/expired (in shares)	(77,200)
Outstanding at end of year (in shares)	770,600	962,500
Exercisable at end of year (in shares)	770,600
Weighted-Average Exercise Price [Roll Forward]
Outstanding at beginning of year (in dollars per share)	$ 41.11
Granted (in dollars per share)	0
Exercised (in dollars per share)	32.82
Forfeited/cancelled/expired (in dollars per share)	77.39
Outstanding at end of year (in dollars per share)	38.71	$ 41.11
Exercisable at end of year (in dollars per share)	$ 38.71
Remaining Contractual Term and Aggregate Intrinsic Value [Abstract]
Outstanding options, weighted-average remaining contractual term	2 years 21 days
Outstanding options, aggregate intrinsic value	$ 13,410
Exercisable options, weighted-average remaining contractual term	2 years 21 days
Exercisable options, aggregate intrinsic value	$ 13,410
Performance-Based Options [Member]
Number of Shares [Roll Forward]
Outstanding at beginning of year (in shares)	2,158,400
Granted (in shares)	1,079,300
Exercised (in shares)	(116,200)
Forfeited/cancelled/expired (in shares)	(723,500)
Outstanding at end of year (in shares)	2,398,000.0	2,158,400
Exercisable at end of year (in shares)	565,600
Weighted-Average Exercise Price [Roll Forward]
Outstanding at beginning of year (in dollars per share)	$ 61.75
Granted (in dollars per share)	30.45
Exercised (in dollars per share)	31.13
Forfeited/cancelled/expired (in dollars per share)	69.82
Outstanding at end of year (in dollars per share)	46.71	$ 61.75
Exercisable at end of year (in dollars per share)	$ 49.26
Remaining Contractual Term and Aggregate Intrinsic Value [Abstract]
Outstanding options, weighted-average remaining contractual term	4 years 10 months 20 days
Outstanding options, aggregate intrinsic value	$ 31,720
Exercisable options, weighted-average remaining contractual term	3 years 18 days
Exercisable options, aggregate intrinsic value	$ 5,713