Tax Credit Transactions Tax Credit Transactions (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Historic Tax Credit Transaction [Member]	Sep. 30, 2012 Historic Tax Credit Transaction [Member]	Sep. 30, 2013 Historic Tax Credit Transaction [Member]	Sep. 30, 2012 Historic Tax Credit Transaction [Member]	Dec. 31, 2012 Historic Tax Credit Transaction [Member]	Nov. 17, 2008 Historic Tax Credit Transaction [Member] sqft	Sep. 30, 2013 New Markets Tax Credit Transaction [Member]	Sep. 30, 2013 U S B [Member] Historic Tax Credit Transaction [Member]	Dec. 31, 2012 U S B [Member] Historic Tax Credit Transaction [Member]	Aug. 27, 2010 U S B [Member] Historic Tax Credit Transaction [Member]	Sep. 30, 2013 U S B [Member] New Markets Tax Credit Transaction [Member]	Dec. 31, 2012 U S B [Member] New Markets Tax Credit Transaction [Member]
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Description											100% recapture for a period of seven years as provided in the Internal Revenue Code
Area Of Irs Campus Building										862,692
Percentage Of Building Leased To Irs										100.00%
Agreed contribution in project cost														$ 64,100,000
Percentage Of Tax Credit Recapture							20.00%				100.00%
Deferred Revenue												26,800,000	39,100,000		13,300,000	13,300,000
Contribution allocated in non controlling interest					2,700,000		2,700,000		2,600,000
Recognition Of Cash Received As Revenue Net Of Allocated Expenses							over the five year credit recapture period as defined in the Internal Revenue Code
Historic tax credit transaction income	(11,853,000)	(11,840,000)	(11,853,000)	(11,840,000)			(11,853,000)
Accretion Of Non Controlling Interest Liability					300,000	300,000	1,000,000	1,000,000
Expected benefit from qualified program											7,800,000
Percentage Of Qualified Investments											39.00%
Deferred costs, net					$ 1,000,000		$ 1,000,000		$ 1,600,000		$ 5,300,000					$ 5,300,000
Rate Of Return On Noncontrolling Interest									2.00%
Limit on tax credit claims under the Community Renewal Tax Relief											up to 39% of qualified investments in qualified, active low-income businesses or ventures
Recognition Of Cash Received As Revenue Net Of Allocated Expenses, Period Credit Recapture in Years							5 years				7 years