Income Taxes (Income Tax Reconciliation) (Details 3) (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
Income Tax Reconciliation [Line Items]
Total provision for income tax	$ 31,000	$ 34,500	$ 17,800	$ 5,100	$ 37,000	$ 23,900	$ 17,200	$ 83,300	$ 78,100	$ 83,200	$ 104,400