Note Net income per common share (Computation of net income (loss) per common share ("EPS"), basic and diluted) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share, Basic and Diluted [Abstract]
Net Income	$ 91,324	$ 92,945
Preferred stock dividends	(931)	(931)
Net income (loss) applicable to common stock	$ 90,393	$ 92,014
Average common shares outstanding	101,696,343	102,932,989
Average potential dilutive common shares	140,869	180,906
Average common shares outstanding - assuming dilution	101,837,212	103,113,895
Net Income per Common Share - Basic	$ 0.89	$ 0.89
Net Income per Common Share - Diluted	$ 0.89	$ 0.89