Subsequent Events Pro Forma Table - subsequent events (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Subsequent Event [Line Items]
Business Acquisition, Pro Forma Revenue	$ 764,913	$ 682,131
Business Acquisition, Pro Forma Net Income (Loss)	142,798	159,365
U.S. Dollar [Member]
Subsequent Event [Line Items]
Line of Credit Facility - Parent Company Revolving Credit Facility	300,000
April 1 capacity [Member] | U.S. Dollar [Member]
Subsequent Event [Line Items]
Line of Credit Facility - Parent Company Revolving Credit Facility	$ 1,500,000