Borrowings (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Short Term Borrowings
Outstanding amount	$ 335,000,000
Federal funds purchased
Short Term Borrowings
Average balance during the year	209,400,000
Weighted average interest rate during the year (as a percent)	0.28%
Maximum amount outstanding at any month end during the year	335,000,000
Outstanding amount	$ 335,000,000	$ 0	$ 0