Income Taxes, Deferred Tax Assets and Liabilities Resulted in Deferred Taxes Table (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Gross deferred tax assets:
Allowance for loan losses	$ 100,891	$ 106,258
Allowance for other losses	11,080	10,906
Accrued liabilities	5,969	6,802
Deferred compensation	33,169	31,677
State net operating losses	7,882	14,154
Nonaccrual interest	1,085	1,901
Net unrealized losses on available-for-sale securities	16,980	219
Net unrealized losses on pension and postretirement benefits	21,218	20,404
Other	8,128	5,811
Total deferred tax assets	206,402	198,132
Gross deferred tax liabilities
FHLB stock dividends	0	2,165
Prepaid expenses	70,943	69,396
Goodwill	27,365	25,770
Mortgage banking activities	17,569	15,704
Deferred loan fee income	16,474	17,770
State deferred taxes	3,800	6,366
Lease financing	1,975	3,042
Bank premises and equipment	7,698	7,491
Other	8,594	9,062
Total deferred tax liabilities	154,418	156,766
Net deferred tax assets	$ 51,984	$ 41,366