Supplemental Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Supplemental Information
Income taxes paid	$ 33,664	$ 38,501	$ 39,448	$ 57,607
Interest paid	10,929	9,866	12,000	12,152
Dividends declared but not paid at year end	15,618	15,992	15,618	15,992
Proceeds from Sale of Available-for-sale Securities, Debt	153,469	197,399	218,572	246,331
Proceeds from Sale of Available-for-sale Securities, Equity	$ 1,739		$ 1,739