Pension Plan (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Pension Plan [Abstract]
Service cost	$ 290,000	$ 285,000	$ 871,000	$ 855,000
Interest cost	1,262,000	1,239,000	3,785,000	3,718,000
Expected return on assets	(1,642,000)	(1,288,000)	(4,925,000)	(3,864,000)
Recognized actuarial loss	607,000	635,000	1,821,000	1,904,000
Net periodic pension cost	517,000	871,000	1,552,000	2,613,000
Total contributions to pension plan			$ 13,700,000