Derivative Financial Instruments (Narrative) (Details) (USD $)				3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Mar. 31, 2012 Interest Expense [Member]	Mar. 31, 2012 Forward Commitments To Sell Mortgage Loans [Member]	Mar. 31, 2012 Interest Rate Swaps [Member]	Mar. 31, 2012 Interest Rate Caps [Member]	Mar. 31, 2012 Cash Flow [Member]	Mar. 31, 2012 Cash Flow [Member] Interest Rate Swaps And Caps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate swaps, aggregate notional amount								$ 225,000,000
Number of interest rate swaps	4						2
Amount reclassified from accumulated other comprehensive income to interest expense				5,800,000
Aggregate notional amount	358,500,000				675,400,000	1,600,000,000			225,000,000
Mortgage loans held-for-sale	350,300,000
Covered call options outstanding	0	0	0
Fair value of interest rate derivatives in a net liability position	46,100,000
Collateral securities	29,400,000
Cash collateral	$ 7,100,000