Commitments and Contingent Liabilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Minimum future rental payments:
2012	$ 4,309,000
2013	4,018,000
2014	3,454,000
2015	2,032,000
2016	1,468,000
Thereafter	7,329,000
Total minimum payments	22,610,000
Operating Leases, Rent Expense, Sublease Rentals	639,000	655,000	591,000
Operating Leases, Rent Expense, Net	4,500,000	4,600,000	4,500,000
consideration related to the West Coast acquisition, shares	12,809,525
Consideration for West Coast acquisition, cash	264,500,000
Potential termination fee related to West Coast acquisition	5,000,000
Commitments to Extend Credit [Member]
Minimum future rental payments:
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability	888,500,000	709,900,000
Standby Letters of Credit [Member]
Minimum future rental payments:
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability	19,500,000	30,900,000
Commercial Letter of Credit [Member]
Minimum future rental payments:
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability	$ 46,000	$ 243,000