Earnings Per Share Narrative (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding stock options (in shares)	1,659,142	2,200,000	1,976,326
Antidilutive securities excluded from EPS computation (in shares)	0	400,000
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from EPS computation (in shares)	109,045	600,000
Performance Vested Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
PVRSUs excluded from EPS calculation due to performance conditions not met (in shares)	338,204	354,167