Reconciliation of Basic and Diluted Shares (Details 2) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Restricted stock units
Antidilutive securities
Number of securities not included in computation of diluted earnings per share (in shares)	0	0	0	0
Stock options
Antidilutive securities
Number of securities not included in computation of diluted earnings per share (in shares)	0	55	0	55
Stock appreciation rights
Antidilutive securities
Number of securities not included in computation of diluted earnings per share (in shares)	283	972	489	1,117
Performance share units
Antidilutive securities
Number of securities not included in computation of diluted earnings per share (in shares)	0	176	0	320