Shareholders' Equity and Earnings Per Share Shareholders' Equity And Earnings Per Share (Other Comprehensive Income Reclassified from AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Other Comprehensive Income Reclassified from AOCI [Line Items]
Gains on available-for-sale securities, net	$ 251	$ 816
Income before taxes	52,286	37,759
Income tax expense	(20,234)	(14,549)
Net income	32,052	23,210
Interest on junior subordinated debentures	3,119	3,157
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Unrealized Gains (Losses) on Securities [Member]
Other Comprehensive Income Reclassified from AOCI [Line Items]
Gains on available-for-sale securities, net	251	816
Income before taxes	251	816
Income tax expense	(100)	(327)
Net income	151	489
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Unrealized Gains (Losses) from Derivative Instruments [Member]
Other Comprehensive Income Reclassified from AOCI [Line Items]
Income before taxes	(1,539)	(1,410)
Income tax expense	612	566
Net income	(927)	(844)
Interest on junior subordinated debentures	$ 1,539	$ 1,410