Commercial Mortgage Banking - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Mortgage Banking [Abstract]
Percentage of controlling interest owned by the company in OMHHF	83.68%
Non-controlling interest	16.32%		16.32%
Number of related party	1
Prepayment costs	$ 2,600,000	$ 2,800,000	$ 4,500,000	$ 13,500,000
Custodial escrow accounts	286,500,000		286,500,000		251,400,000
Uninsured balance relation to escrow accounts	167,700,000		167,700,000
Fair value of servicing rights	41,800,000		41,800,000		40,100,000
Carrying value of loan servicing rights	$ 29,496,000	$ 28,121,000	$ 29,496,000	$ 28,121,000	$ 28,879,000	$ 26,983,000
Servicing rights are amortized using straight-line method	10 years