General Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
New Accounting Pronouncements And Change In Accounting Principals [Line Items]
Deferred policy acquisition costs	$ 191,960	$ 189,633
Accounts payable and accrued liabilities	875,574	665,231
Retained earnings	2,756,166	2,429,818	2,239,863
Policy acquisition costs, net	281,201	266,125	255,136
Other operating expense	359,060	330,557	322,914
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	2,257,895
Policy acquisition costs, net		328,134	322,046
Other operating expense		268,548	256,004
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)	(18,032)
Policy acquisition costs, net		(62,009)	(66,910)
Other operating expense		$ 62,009	$ 66,910