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Line of Credit, Long-Term Debt and Capital Lease Obligations - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Nov. 30, 2018	Dec. 31, 2017	Dec. 31, 2015
Debt Instrument [Line Items]
Line of Credit facility, maturity date	Oct. 31, 2022
Long term debt	$ 1,969,818,000		$ 1,846,133,000
Letters of credit outstanding amount	200,000
Line of Credit facility, available balance	$ 1,300,000,000
Minimum [Member]
Debt Instrument [Line Items]
Commitment fee percentage	0.15%
Maximum [Member]
Debt Instrument [Line Items]
Commitment fee percentage	0.30%
Alternate Base Rate [Member] | Federal Funds Rate [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	Federal Funds Rate plus 1/2 of 1.00%
Alternate Base Rate [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	LIBOR for an interest period of one month plus 1.00%
Debt instrument, variable interest rate	1.00%
Applicable Margin Rate [Member] | LIBOR [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, variable interest rate	0.125%
Applicable Margin Rate [Member] | LIBOR [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, variable interest rate	0.75%
Unsecured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit facility, borrowing capacity	$ 2,000,000,000
Letters of Credit [Member]
Debt Instrument [Line Items]
Line of Credit facility, borrowing capacity	$ 37,500,000
5.25% Senior Unsecured Notes Due 2023 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of debt				$ 750,000,000
Debt instrument interest rate	5.25%			5.25%
Debt instrument maturity date description	Payable semi-annually in arrears on June 1 and December 1
Debt instrument, maturity year	2023
Long term debt	$ 1,234,592,000		$ 740,497,000
5.25% Senior Unsecured Notes Due 2023 [Member] | Change In Control [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	101.00%
5.25% Senior Unsecured Notes Due 2023 [Member] | Redemption in 2019 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	102.625%
5.25% Senior Unsecured Notes Due 2023 [Member] | Redemption in 2020 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	101.313%
5.25% Senior Unsecured Notes Due 2023 [Member] | Redemption in 2021 and Thereafter [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	100.00%
6.25% Senior Unsecured Notes Due 2027 [Member]
Debt Instrument [Line Items]
Aggregate principal amount of debt		$ 500,000,000
Debt instrument interest rate	6.25%	6.25%
Debt instrument maturity date description	Payable semi-annually in arrears on January 15 and July 15
Debt instrument, maturity year	2027
6.25% Senior Unsecured Notes Due 2027 [Member] | Change In Control [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	101.00%
6.25% Senior Unsecured Notes Due 2027 [Member] | Redemption Before 2022 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	100.00%
6.25% Senior Unsecured Notes Due 2027 [Member] | Redemption Before 2022 [Member] | Redeem up to 35% of Aggregate Principal Amount [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	35.00%
Redemption price percentage of aggregate principal amount redeemed	106.25%
6.25% Senior Unsecured Notes Due 2027 [Member] | Redemption in 2022 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	104.688%
6.25% Senior Unsecured Notes Due 2027 [Member] | Redemption in 2023 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	103.125%
6.25% Senior Unsecured Notes Due 2027 [Member] | Redemption in 2024 [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	101.563%
6.25% Senior Unsecured Notes Due 2027 [Member] | Redemption in 2025 and Thereafter [Member]
Debt Instrument [Line Items]
Redemption percentage of principal amount	100.00%

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Debt instrument maturity year.

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The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

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Date the credit facility terminates, in CCYY-MM-DD format.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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