Stockholder Rights Plan (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	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 (in hundredths)	15.00%
Share purchase under right agreement description	Each right allows the holder, other than an “acquiring person,” to purchase one one-hundredth of a share (a unit) of Series A Preferred Stock at an initial purchase price of $97.00 under circumstances described in the rights agreement.
Expiration date of rights	Dec. 01, 2019
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Initial purchase price of unit under right agreement (in dollars per share)	97.00