Loans Receivable, Net Summary of Loans Receivable (Details) - USD ($)		9 Months Ended	12 Months Ended
		Sep. 30, 2016	Dec. 31, 2015
Summary of Loans Receivable
Loans receivable	[1]	$ 5,595,962,000	$ 5,078,681,000
Allowance for loan and lease losses		(132,534,000)	(129,697,000)
Loans receivable, net		$ 5,463,428,000	$ 4,948,984,000
Weighted Average Interest Rate on Loans		4.79%	4.84%
Net deferred fees, costs, premiums, and discounts included in loans receivable		$ 14,765,000	$ 15,529,000
Residential Real Estate | Residential Real Estate
Summary of Loans Receivable
Loans receivable		696,817,000	688,912,000
Allowance for loan and lease losses		(13,911,000)	(14,427,000)
Commercial
Summary of Loans Receivable
Loans receivable		4,222,656,000	3,733,517,000
Commercial | Commercial Real Estate
Summary of Loans Receivable
Loans receivable		2,919,415,000	2,633,953,000
Allowance for loan and lease losses		(67,244,000)	(67,877,000)
Commercial | Other Commercial
Summary of Loans Receivable
Loans receivable		1,303,241,000	1,099,564,000
Allowance for loan and lease losses		(36,579,000)	(32,525,000)
Consumer and Other
Summary of Loans Receivable
Loans receivable		676,489,000	656,252,000
Consumer and Other | Home Equity
Summary of Loans Receivable
Loans receivable		435,935,000	420,901,000
Allowance for loan and lease losses		(8,574,000)	(8,998,000)
Consumer and Other | Other Consumer
Summary of Loans Receivable
Loans receivable		240,554,000	235,351,000
Allowance for loan and lease losses		$ (6,226,000)	$ (5,870,000)

[1] Includes net deferred fees, costs, premiums and discounts of $14,765,000 and $15,529,000 at September 30, 2016 and December 31, 2015, respectively.