CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Unrealized (loss) gain on securities, tax expense (benefit)	$ (1,498)	$ 695	$ (4,859)	$ 2,041
Tax expense	$ 17	$ 92	$ 17	$ 92