Subordinated Debentures (Details) (USD $) In Thousands, unless otherwise specified			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 First Company Statutory Trust 2001 [Member]	Dec. 31, 2012 First Company Statutory Trust 2003 [Member]	Dec. 31, 2012 Glacier Capital Trust II [Member]	Dec. 31, 2012 Citizens (ID) Statutory Trust I [Member]	Dec. 31, 2012 Glacier Capital Trust III [Member]	Dec. 31, 2012 Glacier Capital Trust IV [Member]	Dec. 31, 2012 Bank of the San Juans Bancorporation Trust I [Member]
Terms of Subordinated Debentures
Balance	$ 125,418	$ 125,275	$ 2,955	$ 2,182	$ 46,393	$ 5,155	$ 36,083	$ 30,928	$ 1,722
Rate at December 31, 2012			3.613%	3.56%	3.09%	2.958%	1.63%	1.878%	2.131%
Subordinated debentures variable rate structure			3 mo LIBOR plus 3.30	3 mo LIBOR plus 3.25	3 mo LIBOR plus 2.75	3 mo LIBOR plus 2.65	3 mo LIBOR plus 1.29	3 mo LIBOR plus 1.57	3 mo LIBOR plus 1.82
Maturity Date			Jul. 31, 2031	Mar. 26, 2033	Apr. 07, 2034	Jun. 17, 2034	Apr. 07, 2036	Sep. 15, 2036	Mar. 01, 2037
LIBOR Rate			3.30%	3.25%	2.75%	2.65%	1.29%	1.57%	1.82%