Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income, Before-tax Amount	$ 215,926	$ 172,834	$ 162,992
Net income, Tax (Expense) Benefit	(49,815)	(105,013)	(62,336)
Net income, Net of Tax Amount	166,111	67,821	100,656
Unrealized (losses) gains on available-for- sale securities:
Unrealized holding (losses) gains arising during period, Before-tax Amount	(24,990)	8	(3,609)
Unrealized holding (losses) gains arising during period, Tax (Expense) Benefit	6,081	75	1,274
Unrealized holding (losses) gains arising during period, Net of Tax Amount	(18,909)	83	(2,335)
Reclassification adjustment for (losses) gains included in net income, Before-tax Amount	656	(42)	(982)
Reclassification adjustment for (losses) gains included in net income, Tax (Expense) Benefit	(132)	14	371
Reclassification adjustment for (losses) gains included in net income, Net of Tax Amount	524	(28)	(611)
Net unrealized (losses) gains, Before-tax Amount	(24,334)	(34)	(4,591)
Net unrealized (losses) gains, Tax (Expense) Benefit	5,949	89	1,645
Net unrealized (losses) gains, Net of Tax Amount	(18,385)	55	(2,946)
Amortization of losses included in net income on available-for-sale securities transferred to held to maturity, Before-tax Amount	739	1,069	1,759
Amortization of losses included in net income on available-for-sale securities transferred to held to maturity, Tax (Expense) Benefit	(180)	(401)	(662)
Amortization of losses included in net income on available-for-sale securities transferred to held to maturity, Net of Tax Amount	559	668	1,097
Amortization of losses included in net income on terminated derivative financial instruments that were previously accounted for as cash flow hedges, Before-tax Amount	499	891	1,891
Amortization of losses included in net income on terminated derivative financial instruments that were previously accounted for as cash flow hedges, Tax (Expense) Benefit	(129)	(346)	(736)
Amortization of losses included in net income on terminated derivative financial instruments that were previously accounted for as cash flow hedges, Net of Tax Amount	370	545	1,155
Reclassification of disproportionate tax effect related to terminated and current cash flow hedges, Before - Tax Amount	0	0	0
Reclassification of disproportionate tax effect related to terminated and current cash flow hedges, Tax (Expense) Benefit	0	3,289	0
Reclassification of disproportionate tax effect related to terminated and current cash flow hedges, Net of Tax Amount	0	3,289	0
Net cash flow hedge activity, Before-tax Amount	499	891	1,891
Net cash flow hedge activity, Tax (Expense) Benefit	(129)	2,943	(736)
Net cash flow hedge activity, Net of Tax Amount	370	3,834	1,155
Amendments to defined benefit pension plan, Before-tax Amount	(413)	(700)	(454)
Amendments to defined benefit pension plan, Tax (Expense) Benefit	105	180	177
Amendments to defined benefit pension plan, Net of Tax Amount	(308)	(520)	(277)
Net actuarial gain (loss) on defined benefit pension plans, Before-tax Amount	1,015	(1,819)	(952)
Net actuarial gain (loss) on defined benefit pension plans, Tax (Expense) Benefit	(259)	563	370
Net actuarial gain (loss) on defined benefit pension plans, Net of Tax Amount	756	(1,256)	(582)
Amortization of prior service cost and actuarial losses included in net periodic pension cost for defined benefit pension plans, Before-tax Amount	907	798	855
Amortization of prior service cost and actuarial losses included in net periodic pension cost for defined benefit pension plans, Tax (Expense) Benefit	(247)	(310)	(333)
Amortization of prior service cost and actuarial losses included in net periodic pension cost for defined benefit pension plans, Net of Tax Amount	660	488	522
Net defined benefit pension plan activity, Before-tax Amount	1,509	(1,721)	(551)
Net defined benefit pension plan activity, Tax (Expense) Benefit	(401)	433	214
Net defined benefit pension plan activity, Net of Tax Amount	1,108	(1,288)	(337)
Total other comprehensive (loss) income, Before-tax Amount	(21,587)	205	(1,492)
Total other comprehensive (loss) income, Tax (Expense) Benefit	5,239	3,064	461
Total other comprehensive (loss) income, Net of Tax Amount	(16,348)	3,269	(1,031)
Comprehensive income, Before-tax Amount	194,339	173,039	161,500
Comprehensive income, Tax (Expense) Benefit	(44,576)	(101,949)	(61,875)
Comprehensive income, Net of Tax Amount	$ 149,763	$ 71,090	$ 99,625