Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
ASSETS:
Fixed maturities - available for sale, at market value (amortized cost: 2014, $5,709,509; 2013, $5,116,600)	$ 5,818,116	$ 5,201,921
Fixed maturities - available for sale, at fair value	18,426	19,388
Equity securities - available for sale, at market value (cost: 2014, $15; 2013, $15)	16	13
Equity securities - available for sale, at fair value	1,195,257	1,298,940
Short-term investments	659,017	757,162
Other invested assets (cost: 2014, $405,734; 2013, $385,776)	405,734	385,776
Other invested assets, at fair value	1,574,733	1,515,052
Cash	275,418	316,807
Total investments and cash	9,946,717	9,495,059
Accrued investment income	50,173	50,306
Premiums receivable	1,410,534	1,173,780
Reinsurance receivables - unaffiliated	764,252	530,158
Reinsurance receivables - affiliated	3,597,414	3,062,884
Funds held by reinsureds	181,326	175,526
Deferred acquisition costs	109,742	112,024
Prepaid reinsurance premiums	870,981	673,753
Other assets	295,679	247,505
TOTAL ASSETS	17,226,818	15,520,995
LIABILITIES:
Reserve for losses and loss adjustment expenses	7,784,078	7,653,229
Unearned premium reserve	1,557,559	1,317,147
Funds held under reinsurance treaties	98,979	92,514
Losses in the course of payment	515,011	350,820
Commission reserves	53,257	47,226
Other net payable to reinsurers	1,379,033	1,026,292
6.6% Long term notes due 5/1/2067	238,363	238,361
Accrued interest on debt and borrowings	18,312	4,781
Income taxes	40,985	23,949
Unsettled securities payable	64,624	53,772
Other liabilities	273,505	272,468
Total liabilities	12,673,704	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	359,990	351,051
Accumulated other comprehensive income (loss), net of deferred income tax expense (benefit) of $51,996 at 2014 and $47,195 at 2013	96,564	87,648
Retained earnings	4,096,560	3,751,779
Total stockholder's equity	4,553,114	4,190,478
TOTAL LIABILITIES AND STOCKHOLDER'S EQUITY	17,226,818	15,520,995
Senior Notes 4.868% [Member] | Senior Notes [Member]
LIABILITIES:
Senior notes due	400,000
Senior Notes 5.4% [Member] | Senior Notes [Member]
LIABILITIES:
Senior notes due	$ 249,998	$ 249,958