Employee Benefits (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Total expense recorded for stock based compensation
Total stock based compensation expense	$ 8,579	$ 7,635
Service condition restricted stock expense
Total expense recorded for stock based compensation
Total stock based compensation expense	5,859	5,656
Performance - based restricted stock expense
Total expense recorded for stock based compensation
Total stock based compensation expense	$ 2,720	$ 1,979