Pension Plan (Details) (USD $)	3 Months Ended			6 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Compensation and Retirement Disclosure [Abstract]
Employer contributions		$ 7,500,000
Defined Benefit Plan, Net Periodic Pension Cost [Abstract]
Service cost	69,000		65,000	138,000	130,000
Interest cost on projected benefit obligation	785,000		860,000	1,571,000	1,719,000
Expected return on plan assets	(1,302,000)		(1,131,000)	(2,604,000)	(2,262,000)
Net amortization and deferral	732,000		731,000	1,463,000	1,463,000
Net periodic benefit cost	$ 284,000		$ 525,000	$ 568,000	$ 1,050,000