Offsetting Assets and Liabilities Offsettting Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Offsetting Liabilities [Line Items]
Derivative liabilities, fair value, gross liability	$ 23,974	$ 6,681
Derivative liabilities, fair value, gross amount offset in balance sheet	0	0
Derivative liabilities, fair value, amount not offset against collateral	23,974	6,681
Derivative, Collateral, Right to Reclaim Securities	(1,495)	(1,299)
Derivative, Collateral, Right to Reclaim Cash	(22,479)	(5,382)
Derivative liabilities, fair value, amount offset against collateral	0	0
Repurchase agreements, gross liability	3,447,050	3,580,754
Repurchase agreements, gross amount offset in balance sheet	0	0
Repurchase agreements, amount not offset against collateral	3,447,050	3,580,754
Repurchase agreements, Collateral, Right to Reclaim Securities	(3,447,050)	(3,580,754)
Repurchase agreements, Collateral, Right to Reclaim Cash	0	0
Repurchase agreements, amount offset against collateral	0	0
Total gross liabilities	3,471,024	3,587,435
Total gross liabilities, gross amount offset in balance sheet	0	0
Total liabilities, amount not offset against collateral	3,471,024	3,587,435
Total liabilities, Collateral, Right to Reclaim Securities	(3,448,545)	(3,582,053)
Total liabilities, Collateral, Right to Reclaim Cash	(22,479)	(5,382)
Total liabilities, amount offset against collateral	$ 0	$ 0