Mortgage Banking (Details) (USD $)	3 Months Ended			12 Months Ended
	Mar. 31, 2013	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2012
Mortgage Banking [Abstract]
Gain (loss) on fair value hedge ineffectiveness, net	$ 1,300,000		$ (1,000,000)
Mortgage servicing rights [Abstract]
Balance at beginning of period	47,341,000	45,893,000	43,274,000	43,274,000
Origination of servicing assets	5,521,000		4,477,000
Change in fair value [Abstract]
Due to market changes	1,127,000		248,000
Due to runoff	(2,460,000)		(2,106,000)
Balance at end of period	51,529,000		45,893,000	47,341,000
Period of put back response	60 days
Mortgage loan servicing representation and warranty expenses	590,000		1,900,000
Reserve for mortgage loan servicing put back expenses	$ 7,300,000	$ 4,000,000		$ 7,800,000