Fair Value Measurements - Financial instruments not carried at fair value (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities, held to maturity	$ 2,854,487	$ 2,858,695
Other investments - structured transactions	288,047	294,048
Deposit liabilities	1,497,599	1,509,243
Notes payable and debt	2,262,824	2,263,203
Fair value of held to maturity securities	3,209,175	3,131,235
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities, held to maturity	2,854,487	2,858,695
Other investments - structured transactions	288,047	294,048
Financial Assets	3,142,534	3,152,743
Deposit liabilities	1,497,599	1,509,243
Notes payable and debt	2,262,824	2,263,203
Financial Liabilities	3,760,423	3,772,446
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities, held to maturity	3,209,175	3,131,235
Other investments - structured transactions	306,989	296,799
Financial Assets	3,516,164	3,428,034
Deposit liabilities	1,739,163	1,718,394
Notes payable and debt	2,483,414	2,429,412
Financial Liabilities	$ 4,222,577	$ 4,147,806