General Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
New Accounting Pronouncements And Change In Accounting Principals [Line Items]
Deferred policy acquisition costs	$ 199,401		$ 199,401		$ 189,633
Accounts payable and accrued liabilities	762,038		762,038		665,231
Retained earnings	2,664,745		2,664,745		2,429,818
Policy acquisition costs, net	67,620	57,496	211,554	193,180
Other operating expense	100,458	84,254	268,164	244,491
As originally reported
New Accounting Pronouncements And Change In Accounting Principals [Line Items]
Deferred policy acquisition costs					217,608
Accounts payable and accrued liabilities					675,174
Retained earnings					2,447,850
Policy acquisition costs, net		71,299		239,160
Other operating expense		70,451		198,511
Change
New Accounting Pronouncements And Change In Accounting Principals [Line Items]
Deferred policy acquisition costs					(27,975)
Accounts payable and accrued liabilities					(9,943)
Retained earnings					(18,032)
Policy acquisition costs, net		(13,803)		(45,980)
Other operating expense		$ 13,803		$ 45,980