Pension Plans and Other Postretirement Benefits - Additional Information (Detail) - USD ($)		12 Months Ended
	Nov. 01, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Minimum pension liability		$ 489,660,000
Minimum pension liability adjustment net of tax		$ 296,979,000
Discount rate		4.25%	4.00%
Decrease in minimum liability adjustment			$ 13,367,000
Increase in minimum pension liability adjustment net of tax			8,610,000
Defined contribution pension and retirement savings plans total expense		$ 23,000,000	22,000,000	$ 21,000,000
Annual rate of increase in health care cost assumed for next fiscal year		6.50%
Defined Benefit Plan, ultimate health care cost trend rate		5.00%
Period for decreasing the annual rate		Over 27 years
Defined benefit pension plans		$ 209,878,000
Percentage of total assets		12.90%
Defined benefit plan fair value of plan assets		$ 1,623,635,000	1,503,614,000
Percentage of pension plan assets that is not exceeded by investment in security of single Non-US Government of Government agency		10.00%
Qualified benefit pension plans		$ 0	0
Percentage of eligible employees contribution for Retirement Savings Plan		50.00%
Percentage of employer matching contribution to employee's contribution		75.00%
Maximum employer contribution on Employee's qualified contribution		4.50%
Qualified defined contribution plans expense during the period		$ 34,145,000	32,466,000	31,797,000
Hudson City [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.25%
Long-term rate of return on plan assets	6.50%
Rate of increase in future compensation levels	3.50%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for plan assets, minimum range		45.00%
Target allocations for plan assets, maximum range		80.00%
Defined benefit plan fair value of plan assets		$ 1,059,758,000	1,071,467,000
Total Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for plan assets, minimum range		5.00%
Target allocations for plan assets, maximum range		40.00%
Defined benefit plan fair value of plan assets		$ 284,365,000	230,663,000
Other Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for plan assets, minimum range		5.00%
Target allocations for plan assets, maximum range		30.00%
Defined benefit plan fair value of plan assets		$ 209,878,000	172,026,000
M&T Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets		$ 148,800,000	$ 154,252,000
Percentage of common stock in total plan assets		9.20%	10.20%
Supplemental Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation		$ 161,657,000
Accumulated benefit obligation			$ 135,891,000
Employer contributions		8,367,000	8,076,000
Supplemental Pension Plan [Member] | Hudson City [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation assumed in acquisition		30,439,000
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation		2,004,531,000	1,813,409,000	$ 1,484,193,000
Accumulated benefit obligation		1,951,425,000	$ 1,782,387,000
Projected benefit obligation assumed in acquisition		247,340,000
Minimum pension liability		$ 494,556,000
Discount rate		4.00%	4.75%	3.75%
Long-term rate of return on plan assets		6.50%	6.50%	6.50%
Rate of increase in future compensation levels		4.39%	4.42%	4.50%
Defined benefit plan fair value of plan assets		$ 1,625,134,000	$ 1,505,661,000	$ 1,506,684,000
Employer contributions		8,367,000	8,076,000
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation		121,497,000	$ 67,502,000	$ 60,592,000
Projected benefit obligation assumed in acquisition		56,539,000
Minimum pension liability		$ 4,896,000
Discount rate		4.00%	4.75%	3.75%
Employer contributions		$ 4,022,000	$ 4,266,000