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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	$ 25,414	$ (2,747)	$ 150,842	$ 7,534
Financing Receivable, Allowance for Credit Loss	266,123	112,141	266,123	112,141	$ 250,579	$ 108,671	$ 114,703	$ 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	23,834,889		23,834,889			23,154,988
Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	10,695	11,236	10,695	11,236	12,576	11,154	10,952	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	255,428	100,905	255,428	100,905	$ 238,003	97,517	$ 103,751	$ 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	31,584	(2,747)	153,449	7,534
Funded Loans [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	(1,924)	131	(8,572)	281
Funded Loans [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	33,508	$ (2,878)	162,021	$ 7,253
Off Balance Sheet [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	$ (6,170)		$ (2,607)