Allowance for Credit Losses and Credit Quality of Loans, Allowance for Credit Losses by Portfolio Segments (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Activity in allowance for credit losses by portfolio segment [Roll Forward]
Provision	[1]	$ 29,640	$ 5,807
Balance, end of period	[1]	100,000
ASU 2016-13 [Member]
Activity in allowance for credit losses by portfolio segment [Roll Forward]
Balance, beginning of period		75,999
Charge-offs		(8,226)
Recoveries		2,587
Provision		29,640
Balance, end of period		100,000
ASU 2016-13 [Member] | Commercial Loans [Member]
Activity in allowance for credit losses by portfolio segment [Roll Forward]
Balance, beginning of period		27,156
Charge-offs		(1,020)
Recoveries		228
Provision		15,848
Balance, end of period		42,212
ASU 2016-13 [Member] | Consumer Loans [Member]
Activity in allowance for credit losses by portfolio segment [Roll Forward]
Balance, beginning of period		32,122
Charge-offs		(6,891)
Recoveries		2,235
Provision		10,080
Balance, end of period		37,546
ASU 2016-13 [Member] | Residential [Member]
Activity in allowance for credit losses by portfolio segment [Roll Forward]
Balance, beginning of period		16,721
Charge-offs		(315)
Recoveries		124
Provision		3,712
Balance, end of period		$ 20,242

[1] Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.