Stock-Based Compensation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Summary of stock-based compensation expense
Stock-based compensation expense	$ 1,628	$ 2,832	$ 5,160	$ 7,431
Stock options [Member]
Summary of stock-based compensation expense
Stock-based compensation expense	1,161	2,658	4,343	7,109
Restricted stock units [Member]
Summary of stock-based compensation expense
Stock-based compensation expense	456	174	797	322
Stock appreciation rights [Member]
Summary of stock-based compensation expense
Stock-based compensation expense	$ 11		$ 20