Pension Plan (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Compensation and Retirement Disclosure [Abstract]
Employer contributions	$ 7,500,000
Defined Benefit Plan, Net Periodic Pension Cost [Abstract]
Service cost	68,000	65,000
Interest cost on projected benefit obligation	769,000	859,000
Expected return on plan assets	(1,319,000)	(1,131,000)
Net amortization and deferral	732,000	732,000
Net periodic benefit cost	$ 250,000	$ 525,000