Basis of Presentation (Details Textual) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended				6 Months Ended		12 Months Ended
	Dec. 31, 2011	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2011 Correction [Member]	Dec. 31, 2007 Correction [Member]
Basis of Presentation (Textual)
Increase to current deferred income tax assets	$ 43,032	$ 43,357		$ 43,032	$ 45,704	$ 43,357	$ 45,704		$ 43,032	$ 910	$ 910
Increase to prepaid income taxes	21,598	24,840		21,598	22,394	24,840	22,394		21,598	735	735
Increase to current income taxes payable	167,560	159,481		167,560	178,677	159,481	178,677		167,560	16,676	16,676
Decrease to retained earnings	1,334,476	1,261,501		1,334,476	1,376,026	1,261,501	1,376,026		1,334,476	(9,182)	(9,182)
Decrease to noncurrent deferred income tax liabilities	732,528	687,337		732,528	756,557	687,337	756,557		732,528	(5,849)	(5,849)
Costs related to implementation of plan		4,551			1,831	5,962	2,137		12,971
Total estimated cost of plan								8,870
Fixed exchange ratio of shares	0.50
Legal, professional and other costs incurred in response to unsolicited tender offer		32,060	10,065	2,227	0	42,125	0
Total cost paid						$ 8,087