Stock-Based Compensation - Schedule of Performance Based Unit Programs (Details) - Unvested performance share units shares in Millions	12 Months Ended
	Dec. 31, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU's outstanding (in shares)	0.5
2016 Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU's outstanding (in shares)	0.3
Expected Vesting Threshold (as a percent)	125.00%
2017 Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU's outstanding (in shares)	0.2
Expected Vesting Threshold (as a percent)	100.00%