Mortgage Servicing Rights - Summary of Balance Changes (Details) (USD $) In Thousands, unless otherwise specified				3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012		Mar. 31, 2013 Mortgage servicing rights [Member]	Mar. 31, 2012 Mortgage servicing rights [Member]
Changes in mortgage servicing rights balance
Beginning of period	$ 6,851	$ 6,456	[1]	$ 4,152	$ 2,739
Servicing rights capitalized				768	427
Amortization of servicing rights				(431)	(311)
Changes in valuation allowance				234	212
End of period	6,851	6,456	[1]	4,723	3,067
Mortgage loans serviced for others				$ 648,621	$ 448,139

[1] Note: The consolidated balance sheet at December 31, 2012 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by U. S. generally accepted accounting principles for complete financial statements. See accompanying notes to the unaudited consolidated financial statements.