Shareholders' Equity and Earnings Per Share Shareholders' Equity And Earnings Per Share (Other Comprehensive Income Reclassified from AOCI) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
(Losses) gains on available-for-sale securities, net	$ (33)	$ 251
Interest on junior subordinated debentures	2,004	3,119
Income before taxes	56,340	52,286
Income tax expense	(21,840)	(20,234)
Net income	34,500	32,052
Accumulated Unrealized (Losses) Gains on Securities | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
(Losses) gains on available-for-sale securities, net	(33)	251
Income before taxes	(33)	251
Income tax expense	13	(100)
Net income	(20)	151
Accumulated Unrealized Losses on Derivative Instruments | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest on junior subordinated debentures	493	1,539
Income before taxes	(493)	(1,539)
Income tax expense	196	612
Net income	$ (297)	$ (927)