Shareholders' Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Accumulated other comprehensive loss, Beginning of Period	$ (452,919)	$ (434,685)	$ (456,461)	$ (438,436)
Other comprehensive loss before reclassifications	(182)	(1,583)	258	(783)
Amounts reclassified from accumulated other comprehensive loss	3,002	2,931	6,104	5,882
Accumulated other comprehensive loss, End of Period	(450,099)	(433,337)	(450,099)	(433,337)
Foreign Currency Translation Adjustment [Member]
Accumulated other comprehensive loss, Beginning of Period	(855)	(1,046)	(1,295)	(1,776)
Other comprehensive loss before reclassifications	(182)	(1,456)	258	(726)
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Accumulated other comprehensive loss, End of Period	(1,037)	(2,502)	(1,037)	(2,502)
Unrelized Loss on Available-for-Sale Security [Member]
Accumulated other comprehensive loss, Beginning of Period	0	(156)	0	(226)
Other comprehensive loss before reclassifications	0	(127)	0	(57)
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Accumulated other comprehensive loss, End of Period	0	(283)	0	(283)
Empoyee Benefit Plans [Member]
Accumulated other comprehensive loss, Beginning of Period	(452,064)	(433,483)	(455,166)	(436,434)
Other comprehensive loss before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive loss	3,002	2,931	6,104	5,882
Accumulated other comprehensive loss, End of Period	$ (449,062)	$ (430,552)	$ (449,062)	$ (430,552)