Employee Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Pension Plan [Member]
Net periodic benefit cost
Service cost	$ 1,303	$ 1,282
Interest cost	1,468	1,262
Expected return on plan assets	(1,739)	(1,336)
Amortization of net loss	544	1,106
Net periodic benefit cost	1,576	2,314
Estimated 2014 pension plan contribution, disclosed in prior year 10K			6,260
Contribution by employer	1,750
Postretirement Benefit Plan [Member]
Net periodic benefit cost
Service cost	924	753
Interest cost	586	424
Expected return on plan assets	0	0
Amortization of net loss	224	136
Net periodic benefit cost	$ 1,734	$ 1,313