Pension Benefits (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Components of Net Periodic Benefit Costs for Both Pension Plans
Service cost	$ 1,914,000	$ 1,515,000	$ 3,146,000	$ 2,465,000
Interest cost	468,000	393,000	813,000	689,000
Expected return on plan assets that reduces periodic pension costs	(483,000)	(352,000)	(769,000)	(572,000)
Amortization of prior service costs	5,000	9,000	9,000	9,000
Amortization of net actuarial loss	414,000	293,000	611,000	394,000
Net periodic benefit cost	2,318,000	1,858,000	3,810,000	2,985,000
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%		10.00%
Required contribution to Qualified Pension Plan for the current fiscal year	373,000		373,000
Defined Benefit Plan, Contributions by Employer			$ 4,300,000