Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
ASSETS:
Fixed maturities - available for sale, at market value (amortized cost: 2014, $5,750,381; 2013, $5,116,600)	$ 5,900,397	$ 5,201,921
Fixed maturities - available for sale, at fair value		19,388
Equity securities - available for sale, at market value (cost: 2014, $15; 2013, $15)	15	13
Equity securities - available for sale, at fair value	1,247,792	1,298,940
Short-term investments	673,408	757,162
Other invested assets (cost: 2014, $392,951; 2013, $385,776)	392,951	385,776
Other invested assets, at fair value	1,559,958	1,515,052
Cash	227,033	316,807
Total investments and cash	10,001,554	9,495,059
Accrued investment income	51,380	50,306
Premiums receivable	1,256,740	1,173,780
Reinsurance receivables - unaffiliated	673,999	530,158
Reinsurance receivables - affiliated	3,284,249	3,062,884
Funds held by reinsureds	179,551	175,526
Deferred acquisition costs	104,516	112,024
Prepaid reinsurance premiums	773,401	673,753
Other assets	300,793	247,505
TOTAL ASSETS	16,626,183	15,520,995
LIABILITIES:
Reserve for losses and loss adjustment expenses	7,657,561	7,653,229
Unearned premium reserve	1,418,445	1,317,147
Funds held under reinsurance treaties	96,754	92,514
Losses in the course of payment	502,639	350,820
Commission reserves	37,219	47,226
Other net payable to reinsurers	1,109,597	1,026,292
6.6% Long term notes due 5/1/2067	238,362	238,361
Accrued interest on debt and borrowings	6,133	4,781
Income taxes	83,675	23,949
Unsettled securities payable	72,534	53,772
Other liabilities	269,196	272,468
Total liabilities	12,142,099	11,330,517
Commitments and Contingencies (Note 6)
STOCKHOLDER'S EQUITY:
Common stock, par value: $0.01; 3,000 shares authorized; 1,000 shares issued and outstanding (2014 and 2013)
Additional paid-in capital	357,537	351,051
Accumulated other comprehensive income (loss), net of deferred income tax expense (benefit) of $70,069 at 2014 and $47,195 at 2013	130,128	87,648
Retained earnings	3,996,419	3,751,779
Total stockholder's equity	4,484,084	4,190,478
TOTAL LIABILITIES AND STOCKHOLDER'S EQUITY	16,626,183	15,520,995
Senior Notes 4.868% [Member]
LIABILITIES:
Senior notes due	400,000
Senior Notes 5.4% [Member]
LIABILITIES:
Senior notes due	$ 249,984	$ 249,958