Stock-Based Compensation Plans - Employee Stock Purchase Plan (Details) - Employee Stock Purchase Plan - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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)	15
Stock-based compensation expense	$ 600,000	$ 400,000	$ 400,000