Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards, expiration date									Dec. 31, 2035
Income tax provision	$ (5,867,000)	$ (5,673,000)	$ (4,198,000)	$ (4,013,000)	$ 443,000	$ (3,130,000)	$ (2,952,000)	$ (1,926,000)	$ (19,751,000)	$ (7,565,000)	$ (5,407,000)
Generated Tax credits									28,421,000	17,100,000	13,142,000
Federal NMTC [Member]
Tax Credit Carryforward [Line Items]
Income tax provision									14,200,000	11,400,000	7,900,000
Low-Income Housing tax credits [Member]
Tax Credit Carryforward [Line Items]
Investment in partnership expected to generate Low-Income Housing tax credit									3,700,000	2,500,000	2,800,000
Federal Historic tax credits [Member]
Tax Credit Carryforward [Line Items]
Generated Tax credits									10,500,000	3,200,000	2,200,000
December 2026 Through December 2032 [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	65,200,000								65,200,000
December 2034 [Member]
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	$ 20,900,000								$ 20,900,000
Minimum [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, expiration date									Dec. 31, 2029
Maximum [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, expiration date									Dec. 31, 2033