Stock Option Plans - Narrative (Details)	6 Months Ended
	Jun. 30, 2017 USD ($) compensation_plan $ / shares shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of stock option plans | compensation_plan	2
Option expiration period	10 years
Option vesting period	4 years
Closing share price (in usd per share) | $ / shares	$ 57.98
Granted (in shares) | shares	232,500
Intrinsic value of granted shares | $	$ 0
Weighted average remaining contractual life of the Company's outstanding options	7 years 10 months 24 days
Weighted average remaining contractual life of the Company's exercisable options	6 years 10 months 27 days