Shareholders' Equity - Additional Information (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stockholders Equity Note [Abstract]
Employee Stock Purchase Plan (ESPP): Maximum annual contribution per employee	10.00%
Employee Stock Purchase Plan (ESPP), Shares in ESPP	86,000
Employee Stock Purchase Plan (ESPP), Shares purchased	21,000	29,000	44,000
Employee Stock Purchase Plan (ESPP), Weighted average purchase price	$ 5.87	$ 5.29	$ 4.91
Preferred stock, shares authorized	2,500,000	2,500,000
Preferred stock, par or stated value per share	$ 0.01	$ 0.01
Preferred stock, shares outstanding	0	0