Reconciliation of Basic and Diluted Shares (Details 2) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Restricted stock units
Antidilutive securities
Number of securities not included in computation of diluted earnings per share (in shares)	0	0
Stock options
Antidilutive securities
Number of securities not included in computation of diluted earnings per share (in shares)	0	55
Stock appreciation rights
Antidilutive securities
Number of securities not included in computation of diluted earnings per share (in shares)	696	1,263
Performance share units
Antidilutive securities
Number of securities not included in computation of diluted earnings per share (in shares)	0	467