Income Per Share (Summary Of Basic And Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Per Share [Abstract]
Net income available to common stockholders	$ 138,872	$ 45,615	$ 228,606	$ 126,847
Add: Interest and amortization of debt issuance costs on 2029 Debentures	4,050
Net income available to common stockholders-diluted	$ 142,922	$ 45,615	$ 228,606	$ 126,847
Weighted average shares outstanding-basic	128,427,444	122,026,421	127,771,419	112,995,512
Stock options	58,150	76,774	64,767	74,462
Unvested incentive units	132,195	250,316	119,583	205,247
Effect of dilutive 2029 Debentures	6,683,976
Weighted average shares/units outstanding-diluted	135,301,765	122,353,511	127,955,769	113,275,221
Basic	$ 1.08	$ 0.37	$ 1.79	$ 1.12
Diluted	$ 1.06	$ 0.37	$ 1.79	$ 1.12