Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains (losses) on investment securities available-for-sale	$ 4	$ 963	$ (168)
Income before income taxes	88,563	84,443	83,943
Income tax expense	(31,077)	(26,374)	(28,985)
Net income	57,486	58,069	$ 54,958
Unrealized gains and losses on available-for-sale securities | Amount reclassified from Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains (losses) on investment securities available-for-sale	4	963
Income before income taxes	4	963
Income tax expense	(2)	(361)
Net income	$ 2	$ 602