Deposits (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Summary of deposits
Non-interest bearing deposits	$ 1,191,933	$ 1,010,899
Non-interest Bearing Deposits, Percentage	22.20%	21.00%
NOW accounts	988,984	843,129
NOW accounts, Percentage	18.40%	17.50%
Savings accounts	478,809	404,671
Savings accounts, Percentage	8.90%	8.40%
Money market deposit accounts	931,370	873,562
Money market deposit accounts, Percentage	17.40%	18.10%
Certificate accounts	1,015,491	1,080,917
Certificate accounts, Percentage	19.00%	22.40%
Wholesale deposits	757,874	608,035
Wholesale deposits, Percentage	14.10%	12.60%
Total interest bearing deposits	4,172,528	3,810,314
Total interest bearing deposits, Percentage	77.80%	79.00%
Total deposits	5,364,461	4,821,213
Total deposits, Percentage	100.00%	100.00%
Deposits with a balance of $100,000 and greater
Demand deposits	2,361,528	1,986,757
Certificate accounts	1,044,488	933,183
Total balances of $100,000 and greater	$ 3,406,016	$ 2,919,940