CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Net income	$ 10,558		$ 8,476
Investments available-for-sale:
Net change in unrealized gains (losses) on investments available-for-sale	(3,046)		(1,103)
Related income tax (expense) benefit	1,215		439
Net investment gains reclassified into earnings	56		73
Related income tax expense	(23)		(29)
Net effect on other comprehensive income (loss) for the period	(1,798)		(620)
Defined benefit pension plan:
Recognition of unrealized gain (loss)	364	[1]	350	[1]
Related income tax (expense) benefit	(146)		(140)
Net effect on other comprehensive income (loss) for the period	218		210
Total other comprehensive income	(1,580)		(410)
Comprehensive income	$ 8,978		$ 8,066

[1] This amount is included in the computation of net periodic pension cost, see Note 10