Balance Sheet Offsetting (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Reverse repurchase agreements
Gross Amount Recognized	$ 700,149,000	$ 200,000,000
Gross Amount Offset	(500,041,000)
Net Amount Presented in the Balance Sheet	200,108,000	200,000,000
Gross Amounts Not Offset in the Balance Sheet, Securities Collateral	(200,000,000)	(200,000,000)
Net Amount	108,000
Repurchase agreements
Gross Amount Recognized	500,041,000
Gross Amount Offset	(500,041,000)
Derivatives not designated as hedging instruments
Financial assets
Gross Amount Recognized	47,800,000	47,900,000
Financial liabilities
Gross Amount Recognized	46,200,000	46,300,000
Derivatives not designated as hedging instruments | Securities swaps
Financial assets
Fair Value of Securities Pledged as Collateral	536,500,000
Financial liabilities
Fair Value of Securities Received as Collateral	525,900,000
Derivatives not designated as hedging instruments | Master netting arrangements and similar agreements
Financial assets
Gross Amount Recognized	8,080,000	18,749,000
Gross Amount Offset	(4,500,000)	(13,323,000)
Net Amount Presented in the Balance Sheet	3,580,000	5,426,000
Net Amount	3,580,000	5,426,000
Financial liabilities
Gross Amount Recognized	41,791,000	32,193,000
Gross Amount Offset	(4,500,000)	(13,323,000)
Net Amount Presented in the Balance Sheet	37,291,000	18,870,000
Gross Amounts Not Offset in the Balance Sheet, Securities Collateral	(11,721,000)	(12,376,000)
Gross Amounts Not Offset in the Balance Sheet, Cash Collateral	(17,729,000)	(7,761,000)
Net Amount	7,841,000	(1,267,000)
Total financial assets and total financial liabilities | Master netting arrangements and similar agreements
Financial assets
Gross Amount Recognized	708,229,000	218,749,000
Gross Amount Offset	(504,541,000)	(13,323,000)
Net Amount Presented in the Balance Sheet	203,688,000	205,426,000
Gross Amounts Not Offset in the Balance Sheet, Securities Collateral	(200,000,000)	(200,000,000)
Net Amount	3,688,000	5,426,000
Financial Liabilities
Gross Amount Recognized	541,832,000	32,193,000
Gross Amount Offset	(504,541,000)	(13,323,000)
Net Amount Presented in the Balance Sheet	37,291,000	18,870,000
Gross Amounts Not Offset in the Balance Sheet, Securities Collateral	(11,721,000)	(12,376,000)
Gross Amounts Not Offset in the Balance Sheet, Cash Collateral	(17,729,000)	(7,761,000)
Net Amount	$ 7,841,000	$ (1,267,000)