Significant Accounting Policies Offsetting Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Deposits Paid for Securities Borrowed, at Carrying Value	$ 0	$ 0
Gross Amount of assets as Offset in Statement of Financial Position	0	0
Securities Borrowed	20,992	46,090
Financial Instruments, assets	0	0
Swap A [Member]
Deposits Paid for Securities Borrowed, at Carrying Value	0	0
Gross Amount of assets as Offset in Statement of Financial Position	0	0
Net amount of financial assets	12,031	20,560
Securities Borrowed	12,031	20,560
Financial Instruments, assets	0	0
Swap B [Member]
Deposits Paid for Securities Borrowed, at Carrying Value	0	0
Gross Amount of assets as Offset in Statement of Financial Position	0	0
Net amount of financial assets	11,739	20,011
Securities Borrowed	11,739	20,011
Financial Instruments, assets	0	0
Swap C [Member]
Deposits Paid for Securities Borrowed, at Carrying Value	0	0
Gross Amount of assets as Offset in Statement of Financial Position	0	0
Net amount of financial assets	(1,416)	2,896
Securities Borrowed	(1,416)	2,896
Financial Instruments, assets	0	0
Swap D [Member]
Deposits Paid for Securities Borrowed, at Carrying Value	0	0
Gross Amount of assets as Offset in Statement of Financial Position	0	0
Net amount of financial assets	(1,362)	2,623
Securities Borrowed	(1,362)	2,623
Financial Instruments, assets	0	0
Fair Value, Inputs, Level 2 [Member]
Interest Rate Swap Agreement Fair Value Disclosure	$ 20,992	$ 46,090