Pension Benefits (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Components of Net Periodic Benefit Costs for Both Pension Plans
Service cost	$ 950,000	$ 848,000
Interest cost	296,000	280,000
Expected return on plan assets	(220,000)	(159,000)
Amortization of net actuarial loss	101,000	91,000
Net periodic benefit cost	1,127,000	1,060,000
Percentage in excess of the greater of the benefit obligation or the market-related value of assets, gain and losses amortized (as a percent)	10.00%
Required contribution to Qualified Pension Plan for the current fiscal year	5,400,000
Contribution to the Qualified Pension Plan in the current fiscal year	$ 2,900,000