Employee Benefit Plans (Details) (Defined benefit pension plan, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined benefit pension plan
Summary of net periodic benefit cost
Interest cost on projected benefit obligation	$ 3,710	$ 4,011	$ 4,526
Return on plan assets	(4,509)	(4,783)	(5,046)
Recognized net actuarial loss	6,330	5,487	4,050
Net periodic benefit cost	$ 5,531	$ 4,715	$ 3,530
Actuarial Assumptions Used to Determine Net Cost
Discount rate (as a percent)	3.58%	4.10%	5.18%
Expected return on assets (as a percent)	6.75%	7.00%	7.50%