Mortgage Loans on Real Estate Mortgage Loans by Credit Quality Indicator (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Notes, Loans and Financing Receivable, Gross	$ 2,600,000,000	$ 2,800,000,000
Financing Receivable, by Credit Quality Indicator [Domain]
Financing Receivable, Recorded Investment [Line Items]
Mortgage Loans on Real Estate Performing	2,597,440,000	2,743,068,000
Mortgage Loans on Real Estate In Workout	26,723,000	67,425,000
Mortgage Loans on Real Estate, Principal Amount of Delinquent Loans	0	6,595,000
Mortgage Loans on Real Estate Collateral Dependent	34,720,000	38,923,000
Notes, Loans and Financing Receivable, Gross	2,658,883,000	2,856,011,000
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	34,700,000	45,500,000
Notes, Loans and Financing Receivable, Gross	$ 2,658,883,000	$ 2,856,011,000

Amount before allowance of commercial loans issued to businesses to acquire, develop, construct, improve, or refinance land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph a

-Article 9

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(a))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5066-111524

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(c))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 01-6

-Paragraph 13

-Subparagraph e

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 60

-Paragraph 47

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

-Paragraph 51, 52, 53

-IssueDate 2006-05-01

-Chapter 8

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details