Shareholders' Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, Beginning of Period	$ (450,099)	$ (433,337)	$ (456,461)	$ (438,436)
Other comprehensive income (loss) before reclassifications	305	957	563	174
Amounts reclassified from accumulated other comprehensive loss	3,051	2,928	9,155	8,810
Accumulated other comprehensive loss, End of Period	(446,743)	(429,452)	(446,743)	(429,452)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, Beginning of Period	(1,037)	(2,502)	(1,295)	(1,776)
Other comprehensive income (loss) before reclassifications	305	674	563	(52)
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Accumulated other comprehensive loss, End of Period	(732)	(1,828)	(732)	(1,828)
Unrealized Loss on Available-for-Sale Security [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, Beginning of Period	0	(283)	0	(226)
Other comprehensive income (loss) before reclassifications	0	283	0	226
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Accumulated other comprehensive loss, End of Period	0	0	0	0
Employee Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, Beginning of Period	(449,062)	(430,552)	(455,166)	(436,434)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive loss	3,051	2,928	9,155	8,810
Accumulated other comprehensive loss, End of Period	$ (446,011)	$ (427,624)	$ (446,011)	$ (427,624)