Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Condensed Consolidated Statements of Cash Flows
Net cash provided by operating activities	$ 81,736	$ 13,154
Cash Flows from Investing Activities
Investments purchased	(358,510)	(628,331)
Investments sold	221,133	180,641
Investments called or matured	114,929	469,041
Net change in short-term investments	10,869	(59,088)
Net property and equipment purchased	(10,766)	(11,073)
Net cash used in investing activities	(22,345)	(48,810)
Cash Flows from Financing Activities
Cash dividends paid	(21,354)	(19,940)
Stock plan share issuance	159	4,842
Excess tax benefit from exercise of stock options	4,888	871
Net cash used in financing activities	(16,307)	(14,227)
Net increase (decrease) in cash	43,084	(49,883)
Cash at the beginning of the period	44,314	81,184
Cash at September 30	$ 87,398	$ 31,301