Employee Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2013

Employee Benefit Plans (Tables) [Abstract]

Schedule of the components of net periodic benefit cost

	Three months ended March 31,
	2013		2012
Components of net periodic benefit cost:
Service cost	$	3,851	$	2,692
Interest cost		6,760		6,492
Expected return on plan assets		(3,400)		(3,825)
Amortization of unrealized losses		6,392		4,373
Net periodic benefit costs	$	13,603	$	9,732