Long Term Debt (Parenthetical) (Detail)			12 Months Ended
	Nov. 23, 2015	Feb. 20, 2015	Dec. 31, 2016	Dec. 31, 2015
2.13% and 7.65% due 2016
Debt Instrument [Line Items]
Long-term debt maturity year			2016	2016
2.13% and 7.65% due 2016 | Minimum
Debt Instrument [Line Items]
Interest Rate			2.13%	2.13%
2.13% and 7.65% due 2016 | Maximum
Debt Instrument [Line Items]
Interest Rate			7.65%	7.65%
1.85% due 2018
Debt Instrument [Line Items]
Interest Rate	1.85%		1.85%	1.85%
Long-term debt maturity year	2018		2018	2018
4.25% due 2019
Debt Instrument [Line Items]
Interest Rate			4.25%	4.25%
Long-term debt maturity year			2019	2019
2.50% due 2020
Debt Instrument [Line Items]
Interest Rate	2.50%		2.50%	2.50%
Long-term debt maturity year	2020		2020	2020
3.35% due 2021
Debt Instrument [Line Items]
Interest Rate			3.35%	3.35%
Long-term debt maturity year			2021	2021
3.10% due 2023
Debt Instrument [Line Items]
Interest Rate	3.10%		3.10%	3.10%
Long-term debt maturity year	2023		2023	2023
2.90% Due 2025
Debt Instrument [Line Items]
Interest Rate		2.90%	2.90%	2.90%
Long-term debt maturity year		2025	2025	2025
3.55% due 2026
Debt Instrument [Line Items]
Interest Rate	3.55%		3.55%	3.55%
Long-term debt maturity year	2026		2026	2026
3.60% Due 2035
Debt Instrument [Line Items]
Interest Rate		3.60%	3.60%	3.60%
Long-term debt maturity year		2035	2035	2035
4.50% and 6.15% due 2036
Debt Instrument [Line Items]
Long-term debt maturity year			2036	2036
4.50% and 6.15% due 2036 | Minimum
Debt Instrument [Line Items]
Interest Rate			4.50%	4.50%
4.50% and 6.15% due 2036 | Maximum
Debt Instrument [Line Items]
Interest Rate			6.15%	6.15%
4.85% due 2041
Debt Instrument [Line Items]
Interest Rate			4.85%	4.85%
Long-term debt maturity year			2041	2041
4.07% due 2042
Debt Instrument [Line Items]
Interest Rate			4.07%	4.07%
Long-term debt maturity year			2042	2042
3.80% due 2045
Debt Instrument [Line Items]
Interest Rate		3.80%	3.80%	3.80%
Long-term debt maturity year		2045	2045	2045
4.70% due 2046
Debt Instrument [Line Items]
Interest Rate	4.70%		4.70%	4.70%
Long-term debt maturity year	2046		2046	2046
Other notes with rates from 5.50% to 8.50%, due 2023 to 2040 | Minimum
Debt Instrument [Line Items]
Interest Rate			5.50%	5.50%
Long-term debt maturity year			2023	2023
Other notes with rates from 5.50% to 8.50%, due 2023 to 2040 | Maximum
Debt Instrument [Line Items]
Interest Rate			8.50%	8.50%
Long-term debt maturity year			2040	2040