Capital Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Capital Unit [Line Items]
Preferred stock, par value (dollars per share)	$ 50	$ 50
Cumulative preferred nonvoting stock (as a percent)	4.50%	4.50%
Shares held in treasury (in shares)	23,240,197	23,554,868
Preferred stock included in Treasury shares at cost line of the Consolidated Balance Sheet	$ 305,159	$ 298,143
Common stock, shares authorized	180,000,000	180,000,000
Common stock, par value (dollars per share)	$ 0	$ 0
Common stock, shares issued (in shares)	62,081,391	62,081,391
Common stock, shares outstanding	38,841,194	38,526,523
Stock Issued During Period, Shares, Treasury Stock Reissued	436,549	357,510
4 1/2% Cumulative Preferred Nonvoting Stock
Capital Unit [Line Items]
Preferred stock, shares authorized	100,000
Preferred stock, par value (dollars per share)	$ 50
Cumulative preferred nonvoting stock (as a percent)	4.50%
Preferred stock, callable price per share (dollars per share)	$ 52.50
Preferred stock, shares issued	71,340
Shares held in treasury (in shares)	52,878
Preferred stock included in Treasury shares at cost line of the Consolidated Balance Sheet	$ 1,800
Treasury purchases (in shares)	0	0	0
Second Cumulative Preferred Voting Stock
Capital Unit [Line Items]
Preferred stock, shares authorized	1,000,000
Preferred stock, par value (dollars per share)	$ 10
Preferred stock, shares issued	0	0
Common Stock
Capital Unit [Line Items]
Common stock, shares outstanding	62,081,391	62,081,391	62,081,391	62,081,391
Treasury
Capital Unit [Line Items]
Common stock, shares outstanding	23,240,197	23,554,868	23,858,463	24,344,813
Share Repurchase Program, May 2015 | Common Stock
Capital Unit [Line Items]
Treasury purchases (in shares)	33,465		168,941
Stock repurchased program, authorized amount (up to)	$ 100,000
Share Repurchase Program, May 2015 | Treasury
Capital Unit [Line Items]
Treasury purchases (in shares)	0