Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains on investment securities available-for-sale	$ 1,796	$ 4	$ 963
Income before income taxes	89,126	88,563	84,443
Income tax expense	(31,340)	(31,077)	(26,374)
Net income	57,786	57,486	$ 58,069
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 on investment securities available-for-sale	1,796	4
Income before income taxes	1,796	4
Income tax expense	(674)	(2)
Net income	$ 1,122	$ 2