Income Taxes (Reconciliation of the Differences Between Taxes Computed Using the Statutory Federal Income Tax Rate and Actual Income Tax Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Expense (Benefit) [Abstract]
Income tax expense based upon the Federal statutory rate on income before income taxes									$ 63,046	$ 44,812	$ 35,282
Increase (decrease) in tax resulting from:
Tax-exempt interest, net of interest expense disallowance									(1,294)	(1,139)	(963)
State taxes, net of federal tax benefit									7,811	6,955	3,602
Income earned on bank owned life insurance									(974)	(854)	(795)
Non-deductible compensation costs									1,156	644	707
Meals, entertainment and related expenses									931	802	669
Foreign subsidiary, net									1,991	0	0
Foreign tax credits									(2,177)	0	0
Tax credits									(1,906)	(562)	(704)
Other, net									352	(200)	(320)
Total income tax expense	$ 18,782	$ 19,871	$ 15,734	$ 14,549	$ 12,753	$ 19,844	$ 7,215	$ 10,646	$ 68,936	$ 50,458	$ 37,478