Summary of Characteristics of Interest Rate Swaps (Detail) (USD $) In Thousands, unless otherwise specified			12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Interest Rate Swaps	Dec. 31, 2013 Interest Rate Swaps 0 - 3 years	Dec. 31, 2013 Interest Rate Swaps 3 - 6 years	Dec. 31, 2013 Interest Rate Swaps 6 - 10 years	Dec. 31, 2013 Interest Rate Swaps Greater than 10 years
Derivative Instruments:
Derivative Instruments minimum maturity period				0 years	3 years	6 years	10 years
Derivative Instruments maximum maturity period				3 years	6 years	10 years
Current Notional			$ 52,426,910	$ 24,286,000	$ 8,865,410	$ 15,785,500	$ 3,490,000
Weighted Average Pay Rate	2.14%	2.21%	2.14%	1.83%	2.02%	2.37%	3.62%
Weighted Average Receive Rate	0.20%	0.24%	0.20%	0.18%	0.19%	0.23%	0.20%
Average Years to Maturity			5 years 3 months 4 days	1 year 11 months 23 days	4 years 2 months 9 days	7 years 7 months 28 days	19 years 11 months 5 days