Employee Benefit Plans (Shares Issued in Connection with Stock Compensation Awards) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
New shares issued from available authorized shares	603,842	0	0
Issued from available treasury stock	547,078	1,509,121	337,056
Total	1,150,920	1,509,121	337,056
Proceeds from stock option exercises	$ 67,746	$ 78,866	$ 14,853
Intrinsic value of stock options exercised	38,275	30,935	5,766
Fair value of stock awards/units vested	$ 4,578	$ 3,679	$ 3,728