Consolidated Statements of Comprehensive Income (not audited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement Of Income and Comprehensive Income [Abstract]
Net Income	$ 9,993	$ 7,701	$ 31,423	$ 23,064
Unrealized Gain on Available-for-Sale Securities:
Reversal of Previously Recognized Gains Realized on Sale of Investments and Included in Other Income During Period			(17)	(25)
Gains (Losses) Arising During Period	36	(80)	19	(85)
Income Tax (Expense) Benefit	(13)	28	(1)	39
Change in Unrealized Gains on Available-for-Sale Securities - net-of-tax	23	(52)	1	(71)
Pension and Postretirement Benefit Plans:
Amortization of Unrecognized Postretirement Benefit Losses and Costs (note 12)	51	146	101	291
Income Tax (Expense)	(20)	(59)	(40)	(117)
Pension and Postretirement Benefit Plans - net-of-tax	31	87	61	174
Total Other Comprehensive Income	54	35	62	103
Total Comprehensive Income	$ 10,047	$ 7,736	$ 31,485	$ 23,167