Deposits and Borrowed Funds (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Deposits and Borrowed Funds
Total deposits	$ 23,502,355,000	$ 20,387,582,000
Non-interest bearing deposits	14,260,000,000	11,150,000,000
Interest bearing deposits	9,240,000,000	9,240,000,000
Maturity distribution of time deposits
2013	613,700,000
2014	66,400,000
2015	31,500,000
2016	28,800,000
2017	25,800,000
Thereafter	1,700,000
Total time deposits	767,900,000	911,400,000
Time deposit, $ 100,000 and over
Maturity distribution of time deposits
2013	440,200,000
2014	48,600,000
2015	26,700,000
2016	25,300,000
2017	22,300,000
Thereafter	1,400,000
Total time deposits	564,500,000
Other time deposits
Maturity distribution of time deposits
2013	173,500,000
2014	17,800,000
2015	4,800,000
2016	3,500,000
2017	3,500,000
Thereafter	300,000
Total time deposits	$ 203,400,000