Allowance for Credit Losses (Allowance for Credit Losses Methodology) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Allowance for credit losses on loans and leases
Balance, beginning of period	$ 291,420	$ 144,872	$ 157,629	$ 144,871
Provision for credit losses for loans and leases	81,484	19,352	186,986	33,036
Charge-offs	(19,453)	(16,707)	(43,908)	(33,859)
Recoveries	3,294	3,552	6,039	7,021
Net recoveries (charge-offs)	(16,159)	(13,155)	(37,869)	(26,838)
Balance, end of period	356,745	151,069	356,745	151,069
Reserve for unfunded commitments
Balance, beginning of period	20,927	4,654	5,106	4,523
Provision for credit losses on unfunded commitments (1)	5,441	203	18,024	334
Balance, end of period	26,368	4,857	26,368	4,857
Total allowance for credit losses	383,113	155,926	383,113	155,926
Provision Related to Accrued Interest on Loans Deferred Due to COVID-19			160
Accounting Standards Update 2016-13 [Member]
Allowance for credit losses on loans and leases
Impact of adoption CECL					$ 49,999
Reserve for unfunded commitments
Impact of adoption CECL					3,238
Commercial real estate
Allowance for credit losses on loans and leases
Balance, beginning of period	99,778	47,841	50,847	47,904
Provision for credit losses for loans and leases	52,890	1,324	96,498	3,075
Charge-offs	0	(387)	0	(2,538)
Recoveries	160	219	406	556
Net recoveries (charge-offs)	160	(168)	406	(1,982)
Balance, end of period	152,828	48,997	152,828	48,997
Reserve for unfunded commitments
Balance, beginning of period	15,760	603	534	628
Provision for credit losses on unfunded commitments (1)	5,048	(42)	16,244	(67)
Balance, end of period	20,808	561	20,808	561
Total allowance for credit losses	173,636	49,558	173,636	49,558
Commercial real estate | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses on loans and leases
Impact of adoption CECL					5,077
Reserve for unfunded commitments
Impact of adoption CECL					4,030
Commercial
Allowance for credit losses on loans and leases
Balance, beginning of period	146,607	64,370	73,820	63,957
Provision for credit losses for loans and leases	21,301	16,069	70,974	27,338
Charge-offs	(17,549)	(14,697)	(40,157)	(27,907)
Recoveries	2,256	2,611	3,969	4,965
Net recoveries (charge-offs)	(15,293)	(12,086)	(36,188)	(22,942)
Balance, end of period	152,615	68,353	152,615	68,353
Reserve for unfunded commitments
Balance, beginning of period	2,927	2,347	2,539	2,250
Provision for credit losses on unfunded commitments (1)	(6)	248	869	345
Balance, end of period	2,921	2,595	2,921	2,595
Total allowance for credit losses	155,536	70,948	155,536	70,948
Commercial | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses on loans and leases
Impact of adoption CECL					44,009
Reserve for unfunded commitments
Impact of adoption CECL					(487)
Residential
Allowance for credit losses on loans and leases
Balance, beginning of period	34,251	22,173	24,714	22,034
Provision for credit losses for loans and leases	6,157	1,398	13,342	1,517
Charge-offs	(143)	(67)	(154)	(202)
Recoveries	283	150	547	305
Net recoveries (charge-offs)	140	83	393	103
Balance, end of period	40,548	23,654	40,548	23,654
Reserve for unfunded commitments
Balance, beginning of period	1,741	162	149	160
Provision for credit losses on unfunded commitments (1)	320	(5)	645	(3)
Balance, end of period	2,061	157	2,061	157
Total allowance for credit losses	42,609	23,811	42,609	23,811
Residential | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses on loans and leases
Impact of adoption CECL					2,099
Reserve for unfunded commitments
Impact of adoption CECL					1,267
Consumer & Other
Allowance for credit losses on loans and leases
Balance, beginning of period	10,784	10,488	8,248	10,976
Provision for credit losses for loans and leases	1,136	561	6,172	1,106
Charge-offs	(1,761)	(1,556)	(3,597)	(3,212)
Recoveries	595	572	1,117	1,195
Net recoveries (charge-offs)	(1,166)	(984)	(2,480)	(2,017)
Balance, end of period	10,754	10,065	10,754	10,065
Reserve for unfunded commitments
Balance, beginning of period	499	1,542	1,884	1,485
Provision for credit losses on unfunded commitments (1)	79	2	266	59
Balance, end of period	578	1,544	578	1,544
Total allowance for credit losses	$ 11,332	$ 11,609	$ 11,332	$ 11,609
Consumer & Other | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses on loans and leases
Impact of adoption CECL					(1,186)
Reserve for unfunded commitments
Impact of adoption CECL					$ (1,572)