Derivative Instruments and Hedging Activities Schedule of Interest Rate Swaps Associated with Borrowings (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Derivative, Notional Amount	$ 43,379,217	$ 43,576,146	$ 37,366,610	$ 44,262,605	$ 27,041,328	$ 22,377,656
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	23,628,148	21,663,148	19,619,000	18,485,000	16,685,000	14,070,000
Interest Rate Swap [Member] | Interest Rate Risk Associated with Borrowings [Member]
Derivative [Line Items]
Derivative, Notional Amount	16,590,000		14,425,000
Derivative, Average Fixed Interest Rate	0.848%		0.698%
Derivative, Average Variable Interest Rate	0.228%		0.235%
Derivative, Average Remaining Period Until Maturity	2.82		2.50
Interest Rate Swap [Member] | Interest Rate Risk Associated with Borrowings [Member] | Derivative Maturity Within One Year From Balance Sheet Date [Member]
Derivative [Line Items]
Derivative, Notional Amount	0		3,900,000
Derivative, Average Fixed Interest Rate	0.00%		0.30%
Derivative, Average Variable Interest Rate	0.00%		0.245%
Derivative, Average Remaining Period Until Maturity	0.00		0.76
Interest Rate Swap [Member] | Interest Rate Risk Associated with Borrowings [Member] | Derivative Maturity Over One And Within Two Years From Balance Sheet Date [Member]
Derivative [Line Items]
Derivative, Notional Amount	10,250,000		1,000,000
Derivative, Average Fixed Interest Rate	0.563%		0.383%
Derivative, Average Variable Interest Rate	0.228%		0.244%
Derivative, Average Remaining Period Until Maturity	1.92		1.04
Interest Rate Swap [Member] | Interest Rate Risk Associated with Borrowings [Member] | Derivative Maturity Over Two And Within Three Years From Balance Sheet Date [Member]
Derivative [Line Items]
Derivative, Notional Amount	4,035,000		2,950,000
Derivative, Average Fixed Interest Rate	0.95%		0.626%
Derivative, Average Variable Interest Rate	0.23%		0.246%
Derivative, Average Remaining Period Until Maturity	3.04		2.42
Interest Rate Swap [Member] | Interest Rate Risk Associated with Borrowings [Member] | Derivative Maturity Over Three And Within Four Years From Balance Sheet Date [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,125,000		5,300,000
Derivative, Average Fixed Interest Rate	1.314%		0.92%
Derivative, Average Variable Interest Rate	0.23%		0.217%
Derivative, Average Remaining Period Until Maturity	3.99		3.49
Interest Rate Swap [Member] | Interest Rate Risk Associated with Borrowings [Member] | Derivative Maturity Over Four Years From Balance Sheet Date [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 1,180,000		$ 1,275,000
Derivative, Average Fixed Interest Rate	2.536%		1.406%
Derivative, Average Variable Interest Rate	0.228%		0.242%
Derivative, Average Remaining Period Until Maturity	8.79		5.04