Stock-Based Compensation Plans - Additional Information - Employee Stock Purchase Plan (Details) - USD ($) shares in Thousands		12 Months Ended
	Jul. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Stock Purchase Plan [Abstract]
Award period		1 year
Employee Stock Purchase Plan
Employee Stock Purchase Plan [Abstract]
Percentage of common stock purchase price that employee allowed to purchase at		85.00%
Maximum stock allowed to be purchased by employee in one year, value		$ 25,000
Stock sold by company to employees (in shares)	18
Stock-based compensation expense		$ 700,000	$ 600,000	$ 400,000