Quarterly Results Of Operations (Unaudited) (Summary Of Quarterly Results Of Operations) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 2,547,834		$ 2,534,156		$ 2,644,894		$ 2,598,610		$ 2,622,692	$ 2,702,488	$ 2,608,101	$ 2,448,372	$ 10,325,494	$ 10,381,653	$ 9,047,657
Income (loss) before provision (benefit) for income taxes	110,214		(32,251)		40,025		83,193		90,346	224,751	193,787	235,253	201,181	744,137	789,699
Net income	$ 65,744		$ (7,022)		$ 32,789		$ 50,044		$ 49,755	$ 140,297	$ 143,610	$ 137,245	$ 141,555	$ 470,907	$ 488,907
Income before provision for income taxes, basic (in dollars per share)	$ 1.65		$ (0.48)		$ 0.58		$ 1.19		$ 1.27	$ 3.11	$ 2.67	$ 3.23
Net income, basic (in dollars per share)	0.99		(0.10)		0.48		0.72		0.70	1.94	1.98	1.88	$ 2.08	$ 6.52	$ 6.38
Income before provision for income taxes, diluted (in dollars per share)	1.63	[1]	(0.48)	[1]	0.58	[1]	1.18	[1]	1.25	3.08	2.63	3.18
Net income, diluted (in dollars per share)	$ 0.97	[1]	$ (0.10)	[1]	$ 0.47	[1]	$ 0.71	[1]	$ 0.69	$ 1.92	$ 1.95	$ 1.86	$ 2.05	$ 6.44	$ 6.30

[1] In accordance with earnings per share guidance, diluted per share amounts are computed in the same manner as basic per share amounts when a loss from operations exists.