Pension Benefits (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Components of Net Periodic Benefit Costs for Both Pension Plans
Service cost	$ 1,595,000	$ 1,914,000	$ 3,168,000	$ 3,146,000
Interest cost	688,000	468,000	1,095,000	813,000
Expected return on plan assets that reduces periodic pension costs	(604,000)	(483,000)	(989,000)	(769,000)
Amortization of prior service costs	5,000	5,000	9,000	9,000
Amortization of net actuarial loss	38,000	414,000	344,000	611,000
Net periodic benefit cost	1,722,000	2,318,000	3,627,000	3,810,000
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%
Defined Benefit Plan, Contributions by Employer			$ 5,300,000