Income Per Share (Summary Of Basic And Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Per Share [Abstract]
Net income available to common stockholders	$ 42,977	$ 138,872	$ 47,077	$ 42,657	$ 44,815	$ 45,615	$ 42,021	$ 39,211	$ 271,583	$ 171,662	$ 130,868
Weighted average shares outstanding-basic									127,941,134	115,717,667	98,405,375
Stock options									61,375	72,818	187,834
Class C Units (2007 Grant)											15,050
Unvested incentive units									125,132	216,092	190,771
Excess exchange value of the 2026 Debentures											370,719
Weighted average shares/units outstanding-diluted									128,127,641	116,006,577	99,169,749
Basic	$ 0.33	$ 1.08	$ 0.37	$ 0.34	$ 0.36	$ 0.37	$ 0.38	$ 0.37	$ 2.12	$ 1.48	$ 1.33
Diluted	$ 0.33	$ 1.06	$ 0.37	$ 0.34	$ 0.36	$ 0.37	$ 0.38	$ 0.36	$ 2.12	$ 1.48	$ 1.32