Employee Pension Plans (Details) (Employee Pension Plans, USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Employee Pension Plans
Summary of net periodic benefit cost
Interest cost	$ 916,000	$ 1,005,000
Expected return on plan assets	(1,120,000)	(1,186,000)
Amortization of net loss	1,544,000	1,396,000
Net periodic benefit cost	1,340,000	1,215,000
Company contribution		800,000
Expected contributions remainder of current fiscal year	$ 1,700,000