Consolidated Statements of Income (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest expense related to derivatives reclassified from accumulated other comprehensive income	$ 3,790	$ 3,770	$ 10,674	$ 10,918
Net security gains reclassified from accumulated other comprehensive income	1,679	1,584	5,553	9,732
Income tax expense reclassified from accumulated other comprehensive income	8,725	8,260	22,314	28,196
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Net Gain (Loss) from Derivatives
Interest expense related to derivatives reclassified from accumulated other comprehensive income	308	492	1,005	1,463
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Net Unrealized Investment Gain (Loss)
Net security gains reclassified from accumulated other comprehensive income	1,679	1,586	5,553	9,964
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Other Comprehensive Income (Loss)
Income tax expense reclassified from accumulated other comprehensive income	$ 511	$ 408	$ 1,696	$ 3,171