Tax-Exempt Bond Financings (Detail) (Tax-exempt bonds, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Outstanding balance of Bonds	$ 35,655	$ 38,460
Outstanding standby letters of credit	36,311
Madera Bond
Debt Instrument [Line Items]
Type of Interest Rate	Variable
Maturity Date of Bond	May 01, 2016
Outstanding balance of Bonds		1,800
Tehama Bond
Debt Instrument [Line Items]
Type of Interest Rate	Variable
Interest Rate on Bond at December 31, 2012	0.24%
Maturity Date of Bond	Jun. 01, 2014
Outstanding balance of Bonds	290	370
Outstanding standby letters of credit	294
San Jose Bond - Series 1997 A
Debt Instrument [Line Items]
Type of Interest Rate	Variable
Maturity Date of Bond	Aug. 01, 2012
Outstanding balance of Bonds		160
San Jose Bond - Series 2001 A
Debt Instrument [Line Items]
Type of Interest Rate	Variable
Interest Rate on Bond at December 31, 2012	0.24%
Maturity Date of Bond	Sep. 01, 2016
Outstanding balance of Bonds	1,815	2,580
Outstanding standby letters of credit	2,062
West Valley Bond
Debt Instrument [Line Items]
Type of Interest Rate	Variable
Interest Rate on Bond at December 31, 2012	0.17%
Maturity Date of Bond	Aug. 01, 2018
Outstanding balance of Bonds	15,500	15,500
Outstanding standby letters of credit	15,678
Lemay Washington Bond
Debt Instrument [Line Items]
Type of Interest Rate	Variable
Interest Rate on Bond at December 31, 2012	0.19%
Maturity Date of Bond	Apr. 01, 2033
Outstanding balance of Bonds	15,930	15,930
Outstanding standby letters of credit	16,126
Lemay Olympia Bond
Debt Instrument [Line Items]
Type of Interest Rate	Variable
Interest Rate on Bond at December 31, 2012	0.19%
Maturity Date of Bond	Apr. 01, 2019
Outstanding balance of Bonds	2,120	2,120
Outstanding standby letters of credit	$ 2,151