Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	1 Months Ended					3 Months Ended				3 Months Ended		1 Months Ended	3 Months Ended				1 Months Ended
	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May 31, 2013	Jan. 31, 2013	May 03, 2014	May 04, 2013	Feb. 01, 2014	Feb. 02, 2013	May 03, 2014 Property, Plant and Equipment [Member]	May 04, 2013 Property, Plant and Equipment [Member]	Oct. 31, 2013 New York City Office [Member]	May 03, 2014 New York City Office [Member]	Sep. 30, 2013 New York City Office [Member]	Sep. 30, 2013 Standby Letters of Credit [Member] New York City Office [Member]	May 03, 2014 Standby Letters of Credit [Member] New York City Office [Member]	May 31, 2014 Subsequent Event [Member]
Property, Plant and Equipment [Line Items]
Fair value of cash and cash equivalents considered as Level 1 inputs						$ 595,950,000	$ 714,174,000	$ 423,168,000	$ 646,761,000
Property and equipment purchased but not yet paid										17,800,000	16,500,000
Sales and purchase agreement, property purchase price agreed upon												222,000,000
Sales and purchase agreement, property lease, term												99 years
Escrow deposit														11,100,000
Additional amount deposited to escrow													8,900,000
Letters of credit outstanding, amount															11,100,000
Sales And Purchase Agreement, Down Payment Paid For Property, Percentage												10.00%
Reduction to line of credit																$ 2,200,000
Cash dividend date declared		2013-11	2013-08	2013-05	2013-01
Cash dividends declared per share (in dollars per share)	$ 0.2	$ 0.17	$ 0.17	$ 0.17	$ 0.17	$ 0.2	$ 0										$ 0.20