Allowance for Loan Losses - Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings (Details) - Commercial - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 4,492,232	$ 4,355,395
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 4,278,448	$ 4,169,721
Total percentage of recorded investment in commercial loan	95.20%	95.70%
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 119,119	$ 88,198
Total percentage of recorded investment in commercial loan	2.70%	2.00%
Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 94,665	$ 97,476
Total percentage of recorded investment in commercial loan	2.10%	2.30%
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 2,614,724	$ 2,498,476
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial Real Estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 2,527,128	$ 2,423,742
Total percentage of recorded investment in commercial loan	96.70%	97.00%
Commercial Real Estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 55,256	$ 33,098
Total percentage of recorded investment in commercial loan	2.10%	1.30%
Commercial Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 32,340	$ 41,636
Total percentage of recorded investment in commercial loan	1.20%	1.70%
Commercial And Industrial
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 1,422,297	$ 1,401,035
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial And Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 1,320,246	$ 1,315,507
Total percentage of recorded investment in commercial loan	92.80%	93.90%
Commercial And Industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 49,271	$ 40,409
Total percentage of recorded investment in commercial loan	3.50%	2.90%
Commercial And Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 52,780	$ 45,119
Total percentage of recorded investment in commercial loan	3.70%	3.20%
Commercial Construction
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 455,211	$ 455,884
Total percentage of recorded investment in commercial loan	99.99%	100.00%
Commercial Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 431,074	$ 430,472
Total percentage of recorded investment in commercial loan	94.70%	94.40%
Commercial Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 14,592	$ 14,691
Total percentage of recorded investment in commercial loan	3.20%	3.20%
Commercial Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 9,545	$ 10,721
Total percentage of recorded investment in commercial loan	2.10%	2.40%