Derivative Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2012

Derivative Financial Instruments [Abstract]

Aggregate notional amount and estimated net fair value of derivative instruments

	As of June 30, 2012					As of December 31, 2011
	Notional		Fair Value			Notional		Fair Value
Cash flow hedges:
Interest rate swaps	$	1,554,845	$	(167,104	)	$	1,570,787	$	(181,499	)
Interest rate caps		36,000		997			36,000		1,360
Net fair value	$	1,590,845	$	(166,107	)	$	1,606,787	$	(180,139	)