Notional Amounts of Swap Agreement, Weighted Average Interest Rates and Remaining Term (Detail) - Interest rate swap agreements - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Notional Amount	$ 2,501,000	$ 3,306,000
Weighted Average Fixed Rate	2.02%	2.10%
Remaining Term in Months	48 months	47 months
Less than 1 year
Derivative [Line Items]
Derivative Notional Amount	$ 541,000	$ 725,000
Weighted Average Fixed Rate	1.70%	1.60%
Remaining Term in Months	7 months	7 months
1 year to 2 years
Derivative [Line Items]
Derivative Notional Amount	$ 190,000	$ 591,000
Weighted Average Fixed Rate	1.63%	1.70%
Remaining Term in Months	21 months	19 months
2 years to 3 years
Derivative [Line Items]
Derivative Notional Amount	$ 335,000	$ 400,000
Weighted Average Fixed Rate	1.65%	1.96%
Remaining Term in Months	34 months	30 months
3 years to 4 years
Derivative [Line Items]
Derivative Notional Amount	$ 295,000	$ 220,000
Weighted Average Fixed Rate	1.71%	1.92%
Remaining Term in Months	45 months	43 months
4 years to 5 years
Derivative [Line Items]
Derivative Notional Amount	$ 550,000	$ 205,000
Weighted Average Fixed Rate	2.18%	2.27%
Remaining Term in Months	61 months	57 months
5 years to 7 years
Derivative [Line Items]
Derivative Notional Amount	$ 390,000	$ 475,000
Weighted Average Fixed Rate	2.51%	2.41%
Remaining Term in Months	85 months	73 months
7 years to 10 years
Derivative [Line Items]
Derivative Notional Amount	$ 200,000	$ 690,000
Weighted Average Fixed Rate	2.94%	2.83%
Remaining Term in Months	103 months	104 months