Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassifications out of accumulated other comprehensive income
Gains on investment securities available-for-sale	$ 989	$ 0	$ 790	$ 4
Income before income taxes	22,147	21,281	65,890	66,194
Income tax expense	(7,883)	(7,353)	(23,329)	(23,125)
Net income	14,264	13,928	42,561	43,069
Unrealized gains and losses on available-for-sale securities | Amount Reclassified from Accumulated Other Comprehensive Income
Reclassifications out of accumulated other comprehensive income
Gains on investment securities available-for-sale	989	0	790	4
Income before income taxes	989	0	790	4
Income tax expense	(371)	0	(296)	(2)
Net income	$ 618	$ 0	$ 494	$ 2