Allowance for Credit Losses (Allowance for Credit Losses Methodology) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Allowance for credit losses on loans and leases
Balance, beginning of period	$ 356,745	$ 151,069	$ 157,629	$ 144,871
Provision for credit losses for loans and leases	1,785	23,227	188,771	56,263
Charge-offs	(16,646)	(23,112)	(60,554)	(56,971)
Recoveries	3,165	5,104	9,204	12,125
Net recoveries (charge-offs)	(13,481)	(18,008)	(51,350)	(44,846)
Balance, end of period	345,049	156,288	345,049	156,288
Reserve for unfunded commitments
Balance, beginning of period	26,368	4,857	5,106	4,523
Provision (recapture) for credit losses on unfunded commitments (1)	(2,062)	228	15,962	562
Balance, end of period	24,306	5,085	24,306	5,085
Total allowance for credit losses	369,355	161,373	369,355	161,373
Provision Related to Accrued Interest on Loans Deferred Due to COVID-19	(61)		99
Accounting Standards Update 2016-13 [Member]
Allowance for credit losses on loans and leases
Balance, beginning of period			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	152,828	48,997	50,847	47,904
Provision for credit losses for loans and leases	(18,834)	2,524	77,664	5,599
Charge-offs	0	(497)	0	(3,035)
Recoveries	61	177	467	733
Net recoveries (charge-offs)	61	(320)	467	(2,302)
Balance, end of period	134,055	51,201	134,055	51,201
Reserve for unfunded commitments
Balance, beginning of period	20,808	561	534	628
Provision (recapture) for credit losses on unfunded commitments (1)	(380)	43	15,864	(24)
Balance, end of period	20,428	604	20,428	604
Total allowance for credit losses	154,483	51,805	154,483	51,805
Commercial real estate | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses on loans and leases
Balance, beginning of period			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	152,615	68,353	73,820	63,957
Provision for credit losses for loans and leases	25,603	18,797	96,577	46,135
Charge-offs	(15,426)	(20,457)	(55,583)	(48,364)
Recoveries	2,044	4,263	6,013	9,228
Net recoveries (charge-offs)	(13,382)	(16,194)	(49,570)	(39,136)
Balance, end of period	164,836	70,956	164,836	70,956
Reserve for unfunded commitments
Balance, beginning of period	2,921	2,595	2,539	2,250
Provision (recapture) for credit losses on unfunded commitments (1)	(1,198)	189	(329)	534
Balance, end of period	1,723	2,784	1,723	2,784
Total allowance for credit losses	166,559	73,740	166,559	73,740
Commercial | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses on loans and leases
Balance, beginning of period			44,009
Reserve for unfunded commitments
Impact of adoption CECL					(487)
Residential
Allowance for credit losses on loans and leases
Balance, beginning of period	40,548	23,654	24,714	22,034
Provision for credit losses for loans and leases	(5,641)	1,113	7,701	2,630
Charge-offs	(120)	(305)	(274)	(507)
Recoveries	407	94	954	399
Net recoveries (charge-offs)	287	(211)	680	(108)
Balance, end of period	35,194	24,556	35,194	24,556
Reserve for unfunded commitments
Balance, beginning of period	2,061	157	149	160
Provision (recapture) for credit losses on unfunded commitments (1)	(542)	(55)	103	(58)
Balance, end of period	1,519	102	1,519	102
Total allowance for credit losses	36,713	24,658	36,713	24,658
Residential | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses on loans and leases
Balance, beginning of period			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	10,754	10,065	8,248	10,976
Provision for credit losses for loans and leases	657	793	6,829	1,899
Charge-offs	(1,100)	(1,853)	(4,697)	(5,065)
Recoveries	653	570	1,770	1,765
Net recoveries (charge-offs)	(447)	(1,283)	(2,927)	(3,300)
Balance, end of period	10,964	9,575	10,964	9,575
Reserve for unfunded commitments
Balance, beginning of period	578	1,544	1,884	1,485
Provision (recapture) for credit losses on unfunded commitments (1)	58	51	324	110
Balance, end of period	636	1,595	636	1,595
Total allowance for credit losses	$ 11,600	$ 11,170	11,600	$ 11,170
Consumer & Other | Accounting Standards Update 2016-13 [Member]
Allowance for credit losses on loans and leases
Balance, beginning of period			$ (1,186)
Reserve for unfunded commitments
Impact of adoption CECL					$ (1,572)