Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2014	Jun. 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		7,100,000
Collateral posted with counterparties		28,800,000
Interest Rate Swaps [Member]
Derivative [Line Items]
Accumulated net after-tax losses related to effective cash flow hedges		12,900,000		6,300,000
Estimated amount of interest rate derivatives to be reclassified to interest expense		8,300,000
Recognized a net reduction to interest expense	$ 145,000	$ 100,000	$ 287,000