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		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
(Losses) gains on available-for-sale securities, net	$ (336)	$ 2	$ (369)	$ 253
Interest on junior subordinated debentures	2,042	3,142	4,046	6,261
Income before taxes	63,031	56,250	119,371	108,536
Income tax expense	(24,490)	(21,943)	(46,330)	(42,177)
Net income	38,541	34,307	73,041	66,359
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	(336)	2	(369)	253
Income before taxes	(336)	2	(369)	253
Income tax expense	133	(1)	146	(101)
Net income	(203)	1	(223)	152
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	521	1,583	1,014	3,122
Income before taxes	(521)	(1,583)	(1,014)	(3,122)
Income tax expense	207	630	403	1,242
Net income	$ (314)	$ (953)	$ (611)	$ (1,880)