Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Derivative [Line Items]
Derivative instruments not designated as hedging instruments, liability		$ 25,000,000
Aggregate fair value of net liability position		11,900,000
Collateral posted with counterparties		31,100,000
Interest Rate Swaps [Member]
Derivative [Line Items]
Accumulated net after-tax losses related to effective cash flow hedges		10,600,000		6,300,000
Estimated amount of interest rate derivatives to be reclassified to interest expense		7,500,000
Recognized a net reduction to interest expense	$ 183,000	$ 100,000	$ 470,000