Condensed Consolidated Statements of Other Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net income	$ 10,990	$ 11,257	$ 26,673	$ 26,844
Investments available-for-sale:
Net change in unrealized gains (losses) on investments available-for-sale	2,594	12,221	3,943	25,054
Related income tax expense	(1,035)	(4,875)	(1,573)	(9,992)
Net investment gains reclassified into earnings	296	231	459	283
Related income tax expense	(118)	(92)	(183)	(113)
Net effect on other comprehensive income (loss) for the period	1,737	7,485	2,646	15,232
Defined benefit pension plan:
Recognition of unrealized gain	197	297	896	890
Related income tax expense	(78)	(119)	(357)	(355)
Net effect on other comprehensive income for the period	119	178	539	535
Total other comprehensive income (loss)	1,856	7,663	3,185	15,767
Comprehensive income	$ 12,846	$ 18,920	$ 29,858	$ 42,611