Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Changes in accumulated other comprehensive income (loss) by component, net of tax
Accumulated other comprehensive income (loss) beginning balance period, net of tax	$ 1,203,608,000	$ 957,182,000	$ 994,964,000	$ 935,003,000
Unrealized gains (losses) on debt securities available for sale:
Unrealized holding gains (losses) on debt securities available for sale, Tax Effect	(1,423,000)	860,000	(8,552,000)	3,830,000
Unrealized holding gains (losses) on debt securities available for sale, Net of Tax	3,568,000	(2,159,000)	21,453,000	(9,609,000)
Unrealized gains on debt securities transferred from held to maturity to available for sale, Tax Effect			1,363,000
Unrealized gains on debt securities transferred from held to maturity to available for sale, Net of Tax			3,417,000
Amounts reclassified from accumulated other comprehensive income, Tax Effect	(85,000)		(29,000)
Amounts reclassified from accumulated other comprehensive income, Net of Tax	(212,000)		(75,000)
Unrealized gains (losses) on cash flow hedges:
Unrealized holding gains (losses) on cash flow hedges, Tax Effect	(239,000)		(239,000)
Unrealized holding gains (losses) on cash flow hedges, Net of Tax	(598,000)		(598,000)
Amounts reclassified from accumulated other comprehensive income, Tax Effect	3,000		3,000
Amounts reclassified from accumulated other comprehensive income, Net of Tax	6,000		6,000
Accumulated other comprehensive income (loss) ending balance period, net of tax	1,215,981,000	972,140,000	1,215,981,000	972,140,000
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss) by component, net of tax
Accumulated other comprehensive income (loss) beginning balance period, net of tax	14,627,000	(10,865,000)	(6,812,000)	(2,810,000)
Unrealized gains (losses) on debt securities available for sale:
Tax Cuts and Jobs Act of 2017 reclassification				(605,000)
Unrealized gains (losses) on cash flow hedges:
Accumulated other comprehensive income (loss) ending balance period, before tax	24,325,000	(18,216,000)	24,325,000	(18,216,000)
Accumulated other comprehensive income (loss) ending balance period, tax effect	(6,934,000)	5,192,000	(6,934,000)	5,192,000
Accumulated other comprehensive income (loss) ending balance period, net of tax	17,391,000	(13,024,000)	17,391,000	(13,024,000)
Unrealized gains (losses) on debt securities available for sale
Changes in accumulated other comprehensive income (loss) by component, net of tax
Accumulated other comprehensive income (loss) beginning balance period, before tax	20,459,000	(15,197,000)	(9,528,000)	(4,777,000)
Accumulated other comprehensive income (loss) beginning balance period, tax effect	(5,832,000)	4,332,000	2,716,000	1,967,000
Accumulated other comprehensive income (loss) beginning balance period, net of tax	14,627,000	(10,865,000)	(6,812,000)	(2,810,000)
Unrealized gains (losses) on debt securities available for sale:
Unrealized holding gains (losses) on debt securities available for sale, Before Tax	4,991,000	(3,019,000)	30,005,000	(13,439,000)
Unrealized holding gains (losses) on debt securities available for sale, Tax Effect	(1,423,000)	860,000	(8,552,000)	3,830,000
Unrealized holding gains (losses) on debt securities available for sale, Net of Tax	3,568,000	(2,159,000)	21,453,000	(9,609,000)
Unrealized gains on debt securities transferred from held to maturity to available for sale, Before Tax			4,780,000
Unrealized gains on debt securities transferred from held to maturity to available for sale, Tax Effect			(1,363,000)
Unrealized gains on debt securities transferred from held to maturity to available for sale, Net of Tax			3,417,000
Amounts reclassified from accumulated other comprehensive income, Before Tax	(297,000)		(104,000)
Amounts reclassified from accumulated other comprehensive income, Tax Effect	85,000		29,000
Amounts reclassified from accumulated other comprehensive income, Net of Tax	(212,000)		(75,000)
Tax Cuts and Jobs Act of 2017 reclassification				(605,000)
Unrealized gains (losses) on cash flow hedges:
Accumulated other comprehensive income (loss) ending balance period, before tax	25,153,000	(18,216,000)	25,153,000	(18,216,000)
Accumulated other comprehensive income (loss) ending balance period, tax effect	(7,170,000)	5,192,000	(7,170,000)	5,192,000
Accumulated other comprehensive income (loss) ending balance period, net of tax	17,983,000	$ (13,024,000)	17,983,000	$ (13,024,000)
Unrealized gains (losses) on cash flow hedges
Unrealized gains (losses) on cash flow hedges:
Unrealized holding gains (losses) on cash flow hedges, Before Tax	(837,000)		(837,000)
Unrealized holding gains (losses) on cash flow hedges, Tax Effect	239,000		(239,000)
Unrealized holding gains (losses) on cash flow hedges, Net of Tax	(598,000)		(598,000)
Amounts reclassified from accumulated other comprehensive income, Before Tax	9,000		9,000
Amounts reclassified from accumulated other comprehensive income, Tax Effect	(3,000)		(3,000)
Amounts reclassified from accumulated other comprehensive income, Net of Tax	6,000		6,000
Accumulated other comprehensive income (loss) ending balance period, before tax	(828,000)		(828,000)
Accumulated other comprehensive income (loss) ending balance period, tax effect	236,000		236,000
Accumulated other comprehensive income (loss) ending balance period, net of tax	$ (592,000)		$ (592,000)