Reconciliation of Basic and Diluted Shares - Antidilutive Securities Excluded from Computation of Earnings per Share (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restricted Stock Units (RSUs) [Member]
Antidilutive securities
Number of securities not included in computation of diluted earnings per share (in shares)	739	443	744	0
Stock appreciation rights
Antidilutive securities
Number of securities not included in computation of diluted earnings per share (in shares)	2,472	1,919	2,558	389
Performance share units
Antidilutive securities
Number of securities not included in computation of diluted earnings per share (in shares)	896	685	918	116