Earnings Per Share - Common Shares Related to Stock Options and RSUs Excluded from Calculated Diluted EPS (Parenthetical) (Details) - shares	3 Months Ended				6 Months Ended
	Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	6,851,000	[1]	3,737,000	[2]	6,649,000	[1]	3,747,000	[2]
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	4,801,000	[1]	3,055,000	[2]	4,617,000	[1]	2,963,000	[2]
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	2,050,000	[1]	682,000	[2]	2,032,000	[1]	784,000	[2]
Performance Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	125,000		137,799		125,000		137,799
Performance Shares | Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	125,000		125,000		125,000		125,000
Performance Shares | Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount			12,799				12,799

[1] These totals do not include 125,000 performance-based options representing the right to acquire the equivalent number of shares of common stock for which all targets required to trigger vesting had not been achieved; therefore such awards were excluded from the calculation of weighted average shares used to compute Diluted EPS for those reporting periods.

[2] These totals do not include 125,000 performance-based options and 12,799 performance based RSUs representing the right to acquire 137,799 shares of common stock for which all targets required to trigger vesting had not been achieved; therefore such awards were excluded from the calculation of weighted average shares used to compute Diluted EPS for those reporting periods.