Allowance for Loan Losses - Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings (Details) - Commercial - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 4,355,395	$ 3,836,877
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Pass
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 4,169,721	$ 3,653,344
Total percentage of recorded investment in commercial loan	95.70%	95.20%
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 88,198	$ 83,680
Total percentage of recorded investment in commercial loan	2.00%	2.20%
Substandard
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 97,476	$ 99,853
Total percentage of recorded investment in commercial loan	2.30%	2.60%
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 2,498,476	$ 2,166,603
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial Real Estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 2,423,742	$ 2,094,851
Total percentage of recorded investment in commercial loan	97.00%	96.70%
Commercial Real Estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 33,098	$ 19,938
Total percentage of recorded investment in commercial loan	1.30%	0.90%
Commercial Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 41,636	$ 51,814
Total percentage of recorded investment in commercial loan	1.70%	2.40%
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 1,401,035	$ 1,256,830
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial and Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 1,315,507	$ 1,182,685
Total percentage of recorded investment in commercial loan	93.90%	94.10%
Commercial and Industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 40,409	$ 43,896
Total percentage of recorded investment in commercial loan	2.90%	3.50%
Commercial and Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 45,119	$ 30,249
Total percentage of recorded investment in commercial loan	3.20%	2.40%
Commercial Construction
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 455,884	$ 413,444
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 430,472	$ 375,808
Total percentage of recorded investment in commercial loan	94.40%	90.90%
Commercial Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 14,691	$ 19,846
Total percentage of recorded investment in commercial loan	3.20%	4.80%
Commercial Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 10,721	$ 17,790
Total percentage of recorded investment in commercial loan	2.40%	4.30%