Segment Information (Reconciliation of Total Segment Income from Operations to Consolidated Income before Income Taxes) (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
Segment Reporting [Abstract]
Income from operations	$ 266,602	$ 142,517	$ 695,884	$ 459,120
Interest expense	(3,297)	(11,934)	(14,921)	(35,682)
Debt retirement costs	0	(7,082)	0	(7,082)
Gain from sales of equity securities	0	477	0	16,429
Other (expense) income, net	(287)	1,222	3,137	3,676
Income before income taxes	$ 263,018	$ 125,200	$ 684,100	$ 436,461