Pension Benefits (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Components of Net Periodic Benefit Costs for Both Pension Plans
Service cost	$ 1,572,000	$ 1,232,000	$ 4,718,000	$ 3,697,000
Interest cost	407,000	345,000	1,220,000	1,034,000
Expected return on plan assets that reduces periodic pension costs	(384,000)	(286,000)	(1,153,000)	(858,000)
Amortization of prior service costs	4,000	4,000	13,000	13,000
Amortization of net actuarial loss	306,000	197,000	917,000	591,000
Net periodic benefit cost	1,905,000	1,492,000	5,715,000	4,477,000
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			4,300,000
Required contribution to Qualified Pension Plan for the current fiscal year	$ 373,000		$ 373,000