Stock-based Compensation Plans (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2018 shares
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	18
Performance Shares [Member] | Executive Long-Term Incentive Compensation Plan (the “ELTI Plan”) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	16
Restricted Stock Units (RSUs) [Member] | Executive Long-Term Incentive Compensation Plan (the “ELTI Plan”) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	16