Consolidated Statements of Changes in Common Shareholders' Equity (USD $) In Thousands, unless otherwise specified	3 Months Ended							9 Months Ended		12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Beginning Balance			$ 2,586,218					$ 2,586,218
Net income for the year	30,424	45,134	5,259	(45,375)	93,947	52,047	31,568	80,817	177,562	132,187	117,157
Net income attributable to noncontrolling interest(s)	75	253	97	64	(71)	11	70	425	10	74	7
Dividends paid on redeemable preferred stock	205	206	444	0	222	222	451	855	895	895	917
Repurchase of Class B common stock								4,196	97,545
Cumulative Foreign Currency Translation Adjustment - Net other comprehensive income (loss)	5,639				3,912			(2,061)	3,345
Unrealized Gain on Available-for-Sale Securities - Net other comprehensive income (loss)	563				(3,579)			48,333	19,301
Unrealized Gain on Pensions and Other Postretirement Plans - Net other comprehensive income (loss)	(973)				(1,274)			(990)	(3,270)
Cash Flow Hedge	9				130			155	(695)
Ending Balance	$ 2,732,013			$ 2,586,218				$ 2,732,013		$ 2,586,218