Schedule I - Condensed Financial Information of Parent (Guarantees and Letters of Credit) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Obligations maximum exposure, total	$ 825,000,000
Obligations number of agreements	36
Guarantees
Condensed Financial Statements, Captions [Line Items]
Obligations maximum exposure, total	661,000,000
Obligations number of agreements	21
Letter of Credit
Condensed Financial Statements, Captions [Line Items]
Obligations maximum exposure, total	1,000,000
Obligations number of agreements	3
Cash Collateralized Letters Of Credit
Condensed Financial Statements, Captions [Line Items]
Obligations maximum exposure, total	163,000,000
Obligations number of agreements	12
Parent Company
Condensed Financial Statements, Captions [Line Items]
Letter of credit, fee range minimum	0.20%
Letter of credit, fee range maximum	3.25%
Parent Company | Guarantees
Condensed Financial Statements, Captions [Line Items]
Obligations maximum exposure, total	661,000,000
Obligations number of agreements	21
Parent Company | Guarantees | Minimum
Condensed Financial Statements, Captions [Line Items]
Obligations, individual exposures (minimum less than $1 million)	1,000,000
Parent Company | Guarantees | Maximum
Condensed Financial Statements, Captions [Line Items]
Obligations, individual exposures (minimum less than $1 million)	280,000,000
Parent Company | Letter of Credit
Condensed Financial Statements, Captions [Line Items]
Obligations number of agreements	3
Letters of credit outstanding	1,000,000
Parent Company | Letter of Credit | Minimum
Condensed Financial Statements, Captions [Line Items]
Obligations, individual exposures (minimum less than $1 million)	1,000,000
Parent Company | Cash Collateralized Letters Of Credit
Condensed Financial Statements, Captions [Line Items]
Obligations maximum exposure, total	163,000,000
Obligations number of agreements	12
Parent Company | Cash Collateralized Letters Of Credit | Minimum
Condensed Financial Statements, Captions [Line Items]
Obligations, individual exposures (minimum less than $1 million)	1,000,000
Parent Company | Cash Collateralized Letters Of Credit | Maximum
Condensed Financial Statements, Captions [Line Items]
Obligations, individual exposures (minimum less than $1 million)	$ 109,000,000