v2.4.0.8
Investments - Fair Value and Unrealized Losses (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2014
securities
Dec. 31, 2013
securities
Fair value    
12 Months or More, Fair value   $ 229,896
Total, Fair value   1,582,739
Unrealized losses    
12 Months or More, Unrealized losses   (8,826)
Total, Unrealized losses   (66,373)
Number of securities in loss position (in securities) 103 140
12 Months or More, number of securities (in securities) 24 19
U.S. agency bonds – mortgage-backed [Member]
    
Fair value    
Less than 12 Months, Fair value 743,882 795,439
12 Months or More, Fair value 109,169 60,602
Total, Fair value 853,051 856,041
Unrealized losses    
Less than 12 Months, Unrealized losses (30,320) (38,421)
12 Months or More, Unrealized losses (3,887) (2,683)
Total, Unrealized losses (34,207) (41,104)
Non-U.S. government bonds [Member]
    
Fair value    
Less than 12 Months, Fair value 7,968 9,946
12 Months or More, Fair value 0 0
Total, Fair value 7,968 9,946
Unrealized losses    
Less than 12 Months, Unrealized losses (331) (712)
12 Months or More, Unrealized losses 0 0
Total, Unrealized losses (331) (712)
Other mortgage-backed bonds [Member]
    
Fair value    
Less than 12 Months, Fair value   33,444
12 Months or More, Fair value   0
Total, Fair value   33,444
Unrealized losses    
Less than 12 Months, Unrealized losses   (232)
12 Months or More, Unrealized losses   0
Total, Unrealized losses   (232)
Corporate bonds [Member]
    
Fair value    
Less than 12 Months, Fair value 183,710 463,469
12 Months or More, Fair value 168,371 169,294
Total, Fair value 352,081 632,763
Unrealized losses    
Less than 12 Months, Unrealized losses (6,590) (16,687)
12 Months or More, Unrealized losses (5,062) (6,143)
Total, Unrealized losses (11,652) (22,830)
Municipal bonds – other [Member]
    
Fair value    
Less than 12 Months, Fair value   50,545
12 Months or More, Fair value   0
Total, Fair value   50,545
Unrealized losses    
Less than 12 Months, Unrealized losses   (1,495)
12 Months or More, Unrealized losses   0
Total, Unrealized losses   (1,495)
Available-for-sale securities [Member]
    
Fair value    
Less than 12 Months, Fair value 935,560 1,352,843
12 Months or More, Fair value 277,540 229,896
Total, Fair value 1,213,100 1,582,739
Unrealized losses    
Less than 12 Months, Unrealized losses (37,241) (57,547)
12 Months or More, Unrealized losses (8,949) (8,826)
Total, Unrealized losses $ (46,190) $ (66,373)