Loans Receivable and Allowance for Credit Losses (Allowance for Credit Losses Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable Allowance for Credit Losses
Allowance for loan losses	$ 632,071,000		$ 632,071,000				$ 358,287,000
Increase to allowance for loan losses				$ 273,800,000
Provision for credit losses	102,443,000	$ 19,245,000	176,313,000	41,824,000
Gross charge-offs	0	317,000	0	390,000
PCD or PCI loans
Financing Receivable Allowance for Credit Losses
Allowance for loan losses							0
Commercial and consumer lending
Financing Receivable Allowance for Credit Losses
Allowance for loan losses	632,071,000	330,625,000	632,071,000	330,625,000	$ 557,003,000		358,287,000	$ 317,894,000	$ 311,322,000
Provision for credit losses	94,300,000	20,731,000	168,956,000	41,371,000
Gross charge-offs	20,949,000	11,759,000	33,906,000	29,017,000
Commercial and industrial (“C&I”)
Financing Receivable Allowance for Credit Losses
Allowance for loan losses	756,000		756,000
Commercial and industrial (“C&I”) | Commercial lending
Financing Receivable Allowance for Credit Losses
Allowance for loan losses	380,723,000	205,503,000	380,723,000	205,503,000	$ 362,629,000		238,376,000	$ 189,757,000	$ 189,117,000
Provision for credit losses	37,862,000	26,140,000	98,480,000	41,404,000
Gross charge-offs	$ 20,378,000	$ 11,745,000	$ 32,355,000	$ 28,989,000
Commercial and industrial (“C&I”) | Commercial lending | PCD or PCI loans
Financing Receivable Allowance for Credit Losses
Allowance for loan losses							$ 0
ASU 2016-13
Financing Receivable Allowance for Credit Losses
Allowance for loan losses						$ 125,200,000
ASU 2016-13 | PCD or PCI loans
Financing Receivable Allowance for Credit Losses
Allowance for loan losses						$ 1,200,000