Loans and Allowance for Credit Losses Loans and Allowance for Credit Losses (Balance of ALLL and Related Loans) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	$ 29,232	$ 1,839	$ 180,074	$ 9,373
Provision for Other Credit Losses	616		616
Financing Receivable, Allowance for Credit Loss	274,128	108,462	274,128	108,462	$ 266,123	$ 108,671	$ 112,141	$ 109,931
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment						20,490
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment						88,181
Financing Receivable, Individually Evaluated for Impairment						244,905
Financing Receivable, Collectively Evaluated for Impairment						22,743,323
Loans and Leases Receivable, Net of Deferred Income	23,779,315		23,779,315			23,154,988
Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	16,030	11,399	16,030	11,399	10,695	11,154	11,236	10,788
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment						9
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment						11,145
Financing Receivable, Individually Evaluated for Impairment						57,117
Financing Receivable, Collectively Evaluated for Impairment						5,454,422
Loans and Leases Receivable, Net of Deferred Income						5,661,119
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	258,098	97,063	258,098	97,063	$ 255,428	97,517	$ 100,905	$ 99,143
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment						20,481
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment						77,036
Financing Receivable, Individually Evaluated for Impairment						187,788
Financing Receivable, Collectively Evaluated for Impairment						17,288,901
Loans and Leases Receivable, Net of Deferred Income						17,493,869
Financial Asset Acquired with Credit Deterioration [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss						0
Loans and Leases Receivable, Net of Deferred Income						166,760
Financial Asset Acquired with Credit Deterioration [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss						0
Loans and Leases Receivable, Net of Deferred Income						149,580
Financial Asset Acquired with Credit Deterioration [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss						0
Loans and Leases Receivable, Net of Deferred Income						$ 17,180
Funded Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	27,646	1,839	181,095	9,373
Funded Loans [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	5,331	158	(3,241)	439
Funded Loans [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	22,315	$ 1,681	184,336	$ 8,934
Off Balance Sheet [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	(93)		(2,700)
Accrued Interest Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	1,063		1,063
Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	$ 28,616		$ 179,458