Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Unrealized gains (losses) arising during the period, tax expense (benefit)	$ 13,593	$ (10,121)	$ 2,760
Reclassification adjustment for gains included in net income, tax expense	(4,101)	(269)	(216)
Unrealized gains (losses) arising during the period, tax expense (benefit)	3,469	(3,454)	(92)
Unrealized (losses) gains arising during the period, tax (benefit) expense	$ (7,080)	$ 8,083	$ (3,031)