Allowance for Credit Losses - Activity (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 loan and lease losses:
Balance at beginning of period		$ 141,546	$ 130,530	$ 141,718
Adoption of ASU 2016-13					$ 770
Charge-offs		(9,505)	(34,803)	(18,127)
Recoveries		2,624	5,281	5,394
Increase (decrease) in Provision		3,870	90,342	9,550
Balance at end of period	$ 192,120	138,535	192,120	138,535
Commercial and Industrial
Allowance for loan and lease losses:
Balance at beginning of period	20,884	31,793	28,975	34,501
Adoption of ASU 2016-13					(16,105)
Charge-offs	(13,974)	(2,000)	(14,175)	(2,000)
Recoveries	100	25	320	62
Increase (decrease) in Provision	14,289	1,870	22,284	(875)
Balance at end of period	21,299	31,688	21,299	31,688
Commercial real estate
Allowance for loan and lease losses:
Balance at beginning of period	42,838	21,197	22,325	19,725
Adoption of ASU 2016-13					10,559
Charge-offs	(2,723)		(2,723)
Recoveries		32		63
Increase (decrease) in Provision	13,007	975	22,961	2,416
Balance at end of period	53,122	22,204	53,122	22,204
Construction
Allowance for loan and lease losses:
Balance at beginning of period	8,824	5,381	4,844	5,813
Adoption of ASU 2016-13					(1,803)
Charge-offs	(379)		(379)
Recoveries	30		140
Increase (decrease) in Provision	(3,199)	(367)	2,474	(799)
Balance at end of period	5,276	5,014	5,276	5,014
Lease financing
Allowance for loan and lease losses:
Balance at beginning of period	851	411	424	432
Adoption of ASU 2016-13					207
Charge-offs				(24)
Increase (decrease) in Provision	2,986	35	3,206	38
Balance at end of period	3,837	446	3,837	446
Residential
Allowance for loan and lease losses:
Balance at beginning of period			39,179
Consumer
Allowance for loan and lease losses:
Balance at beginning of period	56,039	35,099	34,644	35,813
Adoption of ASU 2016-13					15,575
Charge-offs	(8,907)	(7,505)	(17,504)	(16,103)
Recoveries	2,456	2,382	4,539	4,834
Increase (decrease) in Provision	17,489	3,662	29,823	9,094
Balance at end of period	67,077	33,638	67,077	33,638
Unallocated
Allowance for loan and lease losses:
Balance at beginning of period	166,013	2,754	139	528
Adoption of ASU 2016-13					(139)
Charge-offs	(25,997)
Recoveries	2,611
Increase (decrease) in Provision	49,493	(629)		1,597
Balance at end of period	192,120	2,125	192,120	2,125
Residential mortgage
Allowance for loan and lease losses:
Balance at beginning of period			29,303
Adoption of ASU 2016-13					(2,793)
Charge-offs			(14)
Recoveries			152
Increase (decrease) in Provision			7,226
Balance at end of period	33,874		33,874
Residential mortgage | Residential
Allowance for loan and lease losses:
Balance at beginning of period	30,021	44,911		44,906
Charge-offs	(14)
Recoveries	17	185		435
Increase (decrease) in Provision	3,850	(1,676)		(1,921)
Balance at end of period	33,874	$ 43,420	33,874	$ 43,420
Home equity
Allowance for loan and lease losses:
Balance at beginning of period			9,876
Adoption of ASU 2016-13					$ (4,731)
Charge-offs			(8)
Recoveries			130
Increase (decrease) in Provision			2,368
Balance at end of period	7,635		7,635
Home equity | Residential
Allowance for loan and lease losses:
Balance at beginning of period	6,556
Recoveries	8
Increase (decrease) in Provision	1,071
Balance at end of period	$ 7,635		$ 7,635