Stock-Based Compensation (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Summary of stock-based compensation expense
Stock-based compensation expense	$ 895	$ 736
Stock appreciation rights [Member]
Summary of stock-based compensation expense
Stock-based compensation expense	331	302
Restricted stock [Member]
Summary of stock-based compensation expense
Stock-based compensation expense	537	403
Employee stock purchase plan [Member]
Summary of stock-based compensation expense
Stock-based compensation expense	$ 27	$ 31