Stock Option and Compensation Plans - Summary of Outstanding RSU Awards Granted (Details) - Restricted stock units shares in Thousands	6 Months Ended
	Jun. 30, 2018 $ / shares shares
Restricted Stock Units
Outstanding, beginning of period (in shares) | shares	327
Vested (in shares) | shares	(65)
Forfeited (in shares) | shares	(63)
Outstanding, end of period (in shares) | shares	199
Weighted Average Grant-Date Fair Value
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 51.08
Vested (in dollars per share) | $ / shares	46.80
Forfeited (in dollars per share) | $ / shares	46.42
Outstanding, end of period (in dollars per share) | $ / shares	$ 53.71