Employee Benefit Plans (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Service cost - benefits earned during the year	$ 2,799	$ 2,073
Interest cost on projected benefit obligations	2,570	2,423
Pension Plans, Defined Benefit [Member]
Service cost - benefits earned during the year	2,799	2,073	1,771
Interest cost on projected benefit obligations	2,570	2,423	2,290
Expected return on plan assets	(3,967)	(3,314)	(2,440)
Net amortization and deferral	1,473	603	616
Net periodic pension cost	$ 2,875	$ 1,785	$ 2,237