Allowance for Loan and Lease Loss and Credit Quality (Non-Accrual Loans and Leases and Loans and Leases Past Due) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 84,591	$ 82,734
Non-Accrual	44,586	50,823
Current	20,276,820	20,289,109
Total, non-covered loans and leases	20,405,997	20,422,666
GNMA Loans past due by 90 days, but not yet repurchased	158
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	123,800	134,500
Greater than 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	33,789	19,766
60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	19,220	17,607
90 Days and Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	31,582	45,361
Commercial real estate | Non-owner occupied term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	6,016	2,234
Non-Accrual	8,438	10,033
Current	3,462,518	3,560,798
Total, non-covered loans and leases	3,476,972	3,573,065
Commercial real estate | Owner occupied term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	4,153	5,293
Non-Accrual	7,231	8,682
Current	2,438,264	2,466,396
Total, non-covered loans and leases	2,449,648	2,480,371
Commercial real estate | Multifamily, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	290	107
Non-Accrual	2,626	4,298
Current	3,300,020	3,300,358
Total, non-covered loans and leases	3,302,936	3,304,763
Commercial real estate | Construction & development, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Non-Accrual	0	0
Current	686,107	736,254
Total, non-covered loans and leases	686,107	736,254
Commercial real estate | Residential development, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Non-Accrual	0	0
Current	205,963	196,890
Total, non-covered loans and leases	205,963	196,890
Commercial real estate | Greater than 30 to 59 Days Past Due | Non-owner occupied term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,044	1,192
Commercial real estate | Greater than 30 to 59 Days Past Due | Owner occupied term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,853	3,920
Commercial real estate | Greater than 30 to 59 Days Past Due | Multifamily, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	290	107
Commercial real estate | Greater than 30 to 59 Days Past Due | Construction & development, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Commercial real estate | Greater than 30 to 59 Days Past Due | Residential development, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Commercial real estate | 60 to 89 Days Past Due | Non-owner occupied term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,972	1,042
Commercial real estate | 60 to 89 Days Past Due | Owner occupied term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,299	1,372
Commercial real estate | 60 to 89 Days Past Due | Multifamily, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Commercial real estate | 60 to 89 Days Past Due | Construction & development, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Commercial real estate | 60 to 89 Days Past Due | Residential development, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Commercial real estate | 90 Days and Accruing | Non-owner occupied term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Commercial real estate | 90 Days and Accruing | Owner occupied term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1	1
Commercial real estate | 90 Days and Accruing | Multifamily, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Commercial real estate | 90 Days and Accruing | Construction & development, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Commercial real estate | 90 Days and Accruing | Residential development, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Commercial | Term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,663	1,109
Non-Accrual	9,315	11,772
Current	2,173,344	2,220,042
Total, non-covered loans and leases	2,185,322	2,232,923
Commercial | Lines of credit & other, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,067	1,512
Non-Accrual	1,684	2,275
Current	1,225,341	1,165,738
Total, non-covered loans and leases	1,229,092	1,169,525
Commercial | Leases & equipment finance, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	21,665	20,341
Non-Accrual	15,292	13,763
Current	1,341,729	1,296,051
Total, non-covered loans and leases	1,378,686	1,330,155
Commercial | Greater than 30 to 59 Days Past Due | Term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,775	992
Commercial | Greater than 30 to 59 Days Past Due | Lines of credit & other, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,625	1,286
Commercial | Greater than 30 to 59 Days Past Due | Leases & equipment finance, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	14,105	8,571
Commercial | 60 to 89 Days Past Due | Term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	195	117
Commercial | 60 to 89 Days Past Due | Lines of credit & other, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	420	143
Commercial | 60 to 89 Days Past Due | Leases & equipment finance, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	7,560	8,754
Commercial | 90 Days and Accruing | Term, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	693	0
Commercial | 90 Days and Accruing | Lines of credit & other, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	22	83
Commercial | 90 Days and Accruing | Leases & equipment finance, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	3,016
Residential | Mortgage, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	38,586	44,118
Non-Accrual	0	0
Current	3,730,369	3,590,955
Total, non-covered loans and leases	3,768,955	3,635,073
Residential | Home equity loans & lines, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,127	3,847
Non-Accrual	0	0
Current	1,165,125	1,172,630
Total, non-covered loans and leases	1,170,252	1,176,477
Residential | Greater than 30 to 59 Days Past Due | Mortgage, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	6,528	0
Residential | Greater than 30 to 59 Days Past Due | Home equity loans & lines, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,981	987
Residential | 60 to 89 Days Past Due | Mortgage, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,507	4,900
Residential | 60 to 89 Days Past Due | Home equity loans & lines, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,421	368
Residential | 90 Days and Accruing | Mortgage, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	28,551	39,218
Residential | 90 Days and Accruing | Mortgage, net | GNMA Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
GNMA Loans past due by 90 days, but not yet repurchased	158	8,900
Residential | 90 Days and Accruing | Home equity loans & lines, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,725	2,492
Consumer & other, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	4,024	4,173
Non-Accrual	0	0
Current	548,040	582,997
Total, non-covered loans and leases	552,064	587,170
Consumer & other, net | Greater than 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,588	2,711
Consumer & other, net | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	846	911
Consumer & other, net | 90 Days and Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 590	$ 551