Securities in an Unrealized Loss Position (Non-Investment Grade Fixed Maturity Securities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Aggregate Fair Value	$ 3,441,075	$ 1,536,923
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Aggregate Fair Value	719,251	543,023
Corporate
Schedule of Available-for-sale Securities [Line Items]
Aggregate Fair Value	1,118,447	469,132
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Aggregate Fair Value	3,407,916	1,450,386
Unrealized Loss Less than 5 Million | Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Number Of Securities	13
Aggregate Fair Value	66,658
Gross Unrealized Loss	3,748
Unrealized Loss Less than 5 Million | Corporate
Schedule of Available-for-sale Securities [Line Items]
Number Of Securities	9
Aggregate Fair Value	31,579
Gross Unrealized Loss	1,005
Unrealized Loss Less than 5 Million | State and Municipal
Schedule of Available-for-sale Securities [Line Items]
Number Of Securities	2
Aggregate Fair Value	23,603
Gross Unrealized Loss	844
Unrealized Loss Less than 5 Million | Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Number Of Securities	24
Aggregate Fair Value	121,840
Gross Unrealized Loss	$ 5,597