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, 2016	Mar. 31, 2015
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Preferred stock dividends	$ (931)	$ (930)
Net income (loss) applicable to common stock	$ 84,068	$ 73,896
Average common shares outstanding	103,188,815	102,939,928
Average potential dilutive common shares	80,998	196,381
Average common shares outstanding - assuming dilution	103,269,813	103,136,309
Net Income per Common Share - Basic	$ 0.81	$ 0.72
Net Income per Common Share - Diluted	$ 0.81	$ 0.72
Continuing Operations
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income (loss) from continuing operations	$ 84,999	$ 73,485
Net income from continuing operations - Basic	$ 0.81	$ 0.71
Net income from continuing operations - Diluted	$ 0.81	$ 0.71
Discontinued Operations
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income Loss From Discontinued Operations Net Of Tax	$ 0	$ 1,341
Net income from discontinued operations - Basic	$ 0	$ 0.01
Net income from discontinued operations - Diluted	$ 0	$ 0.01