Previously Consolidated Variable Interest Entities (Details 12) (USD $) In Thousands, unless otherwise specified			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011 Previously Consolidated Variable Interest Entities Interest Rate Swaps		Dec. 31, 2011 Previously Consolidated Variable Interest Entities Interest Rate Swaps SwissRe		Dec. 31, 2011 Previously Consolidated Variable Interest Entities Interest Rate Swaps Bank of America		Dec. 31, 2011 Previously Consolidated Variable Interest Entities Interest Rate Swaps BankOfAmerica1Member		Dec. 31, 2011 Previously Consolidated Variable Interest Entities Interest Rate Swaps BankOfAmerica2Member
Notional Amount			$ 296,556		$ 236,355		$ 44,562		$ 10,535		$ 5,104
Fair Value		$ 33,759	$ (24,942)		$ (20,540)		$ (2,368)		$ (1,461)		$ (573)
Interest Rate			5.00%	[1]	5.10%	[1]	4.58%	[1]	5.05%	[1]	4.12%	[1]
Derivative Counterparty					Swiss RE Financial		Bank of America		Bank of America		Bank of America
Derivative Maturity			Dec. 31, 2015		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2016		Dec. 31, 2016

[1] Represents the gross fixed interest rate we pay to our counterparties under these derivative instruments. We receive an amount of interest indexed to one-month LIBOR on all of our interest rate swaps.