Mortgage Loans on Real Estate (Mortgage Loan Portfolio Summarized by Geographic Region and Property Type) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	$ 2,607,698	$ 2,658,883	$ 2,856,011
Percent	100.00%	100.00%
East [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	765,717	732,762
Percent	29.40%	27.50%
Middle Atlantic [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	156,489	155,094
Percent	6.00%	5.80%
Mountain [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	356,246	387,599
Percent	13.70%	14.60%
New England [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	21,324	26,385
Percent	0.80%	1.00%
Pacific [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	317,431	320,982
Percent	12.20%	12.10%
South Atlantic [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	483,852	458,802
Percent	18.50%	17.30%
West North Central [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	351,794	370,168
Percent	13.50%	13.90%
West South Central [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	154,845	207,091
Percent	5.90%	7.80%
Office [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	590,414	666,467
Percent	22.60%	25.10%
Medical Office [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	125,703	136,764
Percent	4.80%	5.10%
Retail [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	711,364	677,951
Percent	27.30%	25.50%
Industrial/Warehouse [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	673,449	692,637
Percent	25.80%	26.10%
Hotel [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	61,574	94,045
Percent	2.40%	3.50%
Apartment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	291,823	219,335
Percent	11.20%	8.20%
Mixed Use/Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal outstanding	$ 153,371	$ 171,684
Percent	5.90%	6.50%

Mortgage Loans on Real Estate (Mortgage Loan Portfolio Summarized by Geographic Region and Property Type) (Details) (USD $)
In Thousands, unless otherwise specified

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

$ 2,607,698

$ 2,658,883

$ 2,856,011

Percent

100.00%

East [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

765,717

732,762

Percent

29.40%

27.50%

Middle Atlantic [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

156,489

155,094

Percent

6.00%

5.80%

Mountain [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

356,246

387,599

Percent

13.70%

14.60%

New England [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

21,324

26,385

Percent

0.80%

1.00%

Pacific [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

317,431

320,982

Percent

12.20%

12.10%

South Atlantic [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

483,852

458,802

Percent

18.50%

17.30%

West North Central [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

351,794

370,168

Percent

13.50%

13.90%

West South Central [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

154,845

207,091

Percent

5.90%

7.80%

Office [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

590,414

666,467

Percent

22.60%

25.10%

Medical Office [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

125,703

136,764

Percent

4.80%

5.10%

Retail [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

711,364

677,951

Percent

27.30%

25.50%

Industrial/Warehouse [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

673,449

692,637

Percent

25.80%

26.10%

Hotel [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

61,574

94,045

Percent

2.40%

3.50%

Apartment [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

291,823

219,335

Percent

11.20%

8.20%

Mixed Use/Other [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Principal outstanding

$ 153,371

$ 171,684

Percent

5.90%

6.50%

- Definition

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.

+ References+ Details