CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Unrealized (loss) gain on securities, tax expense (benefit)	$ (3,900)	$ 343	$ (3,361)	$ 1,346
Tax expense	$ 17	$ 92	$ 17	$ 92