Employee Benefit Plans (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Components of Net Periodic Benefit Cost
Service cost	$ 3,162,000	$ 4,473,000	$ 9,066,000	$ 11,676,000
Interest cost	6,839,000	6,340,000	20,811,000	18,939,000
Expected return on plan assets	(4,842,000)	(4,065,000)	(14,532,000)	(12,196,000)
Recognized net actuarial loss	49,000	2,280,000	499,000	6,381,000
Net periodic benefit cost	5,208,000	9,028,000	15,844,000	24,800,000
Employer contribution	$ 2,300,000	$ 11,900,000	$ 8,900,000	$ 18,600,000