Shareholders' Equity - Summary of Preferred and Common Share Activity (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Increase (Decrease) in Stockholders' Equity
Common stock issued, beginning balance	124,218,183
Treasury stock, beginning balance	(9,625,104)
Grants of restricted stock	177,493	169,870	186,961
Vesting of performance shares	191,641	153,360	306,802
Issuance of common stock due to exercise of stock options	897,622	1,661,808	2,184,169
Common stock issued, ending balance	121,218,183	124,218,183
Treasury stock, ending balance	(10,525,147)	(9,625,104)
Common Stock
Increase (Decrease) in Stockholders' Equity
Common stock issued, beginning balance	124,218,183	127,218,183.000	130,218,183
Treasury stock, beginning balance	(9,625,104)	(9,187,075.000)	(7,848,231)
Grants of restricted stock	10,805	9,135	12,549
Forfeitures of restricted stock	7,500
Issuance of common stock due to exercise of stock options	897,622	1,661,808	2,184,169
Treasury stock acquired	(4,950,868)	(5,228,868)	(6,694,582)
Retirement of treasury stock	3,000,000	3,000,000	3,000,000
Common stock issued, ending balance	121,218,183.000	124,218,183	127,218,183.000
Treasury stock, ending balance	(10,525,147.000)	(9,625,104)	(9,187,075.000)
Performance Shares
Increase (Decrease) in Stockholders' Equity
Grants of restricted stock	159,000	153,000	167,500
Performance Shares | Common Stock
Increase (Decrease) in Stockholders' Equity
Vesting of performance shares	149,898	119,896	159,020