Stockholder Rights Plan (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2009
Class of Stock [Line Items]
Number of stock purchase right for each share as dividends under plan (in shares)		1
Percentage of stock acquisition for exercise of rights as specified in right agreement	15.00%
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Number of shares to be purchased by each right exercised (in shares)	0.01
Initial purchase price of unit under right agreement (in dollars per share)	$ 97.00