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Notes Payable - Additional Information (Detail) - USD ($) |  |  |  |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Jun. 16, 2021 | Mar. 17, 2021 | Mar. 31, 2020 | Nov. 05, 2015 | Dec. 31, 2021 | Dec. 31, 2020 | Mar. 30, 2020 | Mar. 31, 2016
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Consolidated Fixed Charge Coverage Ratio |  |  |  |  | 2.50% |  |  |
Consolidated Fixed Charge Coverage Ratio, actual |  |  |  |  | 4.08% |  |  |
Consolidated Leverage Ratio |  |  |  |  | 275.00% |  |  |
Consolidated Leverage Ratio, actual |  |  |  |  | 173.00% |  |  |
Senior notes principal balance outstanding |  |  |  |  | $ 426,500,000 | $ 222,771,000 |  |
Note Purchase Agreement [Member] | Notes Issued March 17, 2014 and Due March 17, 2021 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Proceeds from issuance of senior notes |  |  | $ 40,000,000.0 |  |  |  |  |
Senior notes interest rate |  |  | 3.68% |  |  |  |  |
Debt instrument, maturity date |  |  |  |  | Mar. 17, 2021 |  |  |
Note Purchase Agreement [Member] | Notes Issued November 5, 2015 and Due November 5, 2022 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Proceeds from issuance of senior notes |  |  | $ 60,000,000.0 |  |  |  |  |
Senior notes interest rate |  |  | 3.84% |  |  |  |  |
Debt instrument, maturity date |  |  |  |  | Nov. 05, 2022 |  |  |
Shelf Notes [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Proceeds from issuance of senior notes |  |  | $ 250,000,000 |  |  |  |  |
Senior notes description |  |  |  |  | In addition, pursuant to the Note Purchase Agreement, the Company may authorize the issuance and sale of additional senior notes (the “Shelf Notes”) in the aggregate principal amount of (x) $250 million minus (y) the amount of other notes (such as the Series B Senior Notes and Series C Senior Notes, each defined below) then outstanding, to be dated the date of issuance thereof, to mature, in case of each Shelf Note so issued, no more than 15 years after the date of original issuance thereof, to have an average life, in the case of each Shelf Note so issued, of no more than 15 years after the date of original issuance thereof, to bear interest on the unpaid balance thereof from the date thereof at the rate per annum, and to have such other particular terms, as shall be set forth, in the case of each Shelf Note so issued, in accordance with the Note Purchase Agreement. |  |  |
3.84% Series C senior notes due in 2022 [Member] | Series C Senior Notes [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Proceeds from issuance of senior notes |  |  |  | $ 60,000,000.0 |  |  |  |
Senior notes interest rate |  |  |  | 3.84% | 3.84% | 3.84% |  |
Debt instrument, maturity date |  |  |  |  | Nov. 05, 2022 |  |  |
Senior notes description |  |  |  |  | Interest on the Series C Senior Notes is payable semi-annually beginning on May 5, 2016 and continuing thereafter on November 5 and May 5 of each year until maturity. |  |  |
Senior notes interest payment |  |  |  |  | semi-annually |  |  |
Debt instrument, date of first required payment |  |  |  |  | May 05, 2016 |  |  |
Senior notes principal balance outstanding |  |  |  |  | $ 60,000,000 | $ 60,000,000 |  |
2.57% Series D senior notes due in 2028 [Member] | Series C Senior Notes [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Proceeds from issuance of senior notes |  | $ 40,000,000 |  |  |  |  |  |
Senior notes interest rate |  | 2.57% |  |  | 2.57% |  |  |
Debt instrument, maturity date |  |  |  |  | Mar. 17, 2028 |  |  |
Senior notes description |  |  |  |  | Interest on the Series D Senior Notes is payable semi-annually beginning on September 17, 2021 and continuing thereafter on March 17 and September 17 of each year until maturity. |  |  |
Senior notes interest payment |  |  |  |  | semi-annually |  |  |
Debt instrument, date of first required payment |  |  |  |  | Sep. 17, 2021 |  |  |
Senior notes principal balance outstanding |  |  |  |  | $ 40,000,000 |  |  |
Notes payable amount net |  |  |  |  | $ 40,000,000 |  |  |
2.35% Series E senior notes due in 2026 [Member] | Series E Senior Notes [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Proceeds from issuance of senior notes | $ 60,000,000 |  |  |  |  |  |  |
Senior notes interest rate | 2.35% |  |  |  | 2.35% |  |  |
Debt instrument, maturity date |  |  |  |  | Jun. 16, 2026 |  |  |
Senior notes description |  |  |  |  | Interest on the Series E Senior Notes is payable semi-annually beginning on December 16, 2021 and continuing thereafter on June 16 and December 16 of each year until maturity. |  |  |
Senior notes interest payment |  |  |  |  | semi-annually |  |  |
Debt instrument, date of first required payment |  |  |  |  | Dec. 16, 2021 |  |  |
Senior notes principal balance outstanding |  |  |  |  | $ 60,000,000 |  |  |
Credit Facility [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Credit facility, maximum |  |  | 420,000,000.0 |  |  |  |  |
Revolving credit facility, maturity date |  |  |  |  | Mar. 31, 2025 |  |  |
Additional senior notes indebtedness |  |  | 250,000,000.0 |  |  |  |  |
Consolidated Fixed Charge Coverage Ratio |  |  |  |  | 2.50% |  |  |
Consolidated Fixed Charge Coverage Ratio, actual |  |  |  |  | 4.08% |  |  |
Consolidated Leverage Ratio |  |  |  |  | 275.00% |  |  |
Consolidated Leverage Ratio, actual |  |  |  |  | 173.00% |  |  |
Debt instrument description of variable rate basis |  |  |  |  | (i) LIBOR plus a defined margin, or (ii) the Agent bank’s prime rate (“base rate”) plus a margin. The applicable margin for each type of loan is measured based upon the Consolidated Leverage Ratio at the end of the prior fiscal quarter and ranges from 1.00% to 1.75% for LIBOR loans and 0% to 0.75% for base rate loans. In addition, the Company pays an unused commitment fee for the portion of the $420.0 million credit facility that is not used. These fees are based upon the Consolidated Leverage Ratio and range from 0.15% to 0.30%. As of December 31, 2021 and 2020, the applicable margins were 1.25% for LIBOR based loans, 0.25% for base rate loans and 0.20% for unused fees. Amounts borrowed under the Sweep Service Facility are based upon the MUFG Union Bank, N.A. base rate plus an applicable margin and an unused commitment fee for the portion of the $12.0 million facility not used. |  |  |
Unused commitment fees |  |  |  |  | $ 420,000,000.0 |  |  |
Credit Facility [Member] | Unused Fees [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt instrument interest rate at period end |  |  |  |  | 0.20% | 0.20% |  |
Credit Facility [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Leverage ratio |  |  |  |  | 0.15% |  |  |
Credit Facility [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Leverage ratio |  |  |  |  | 0.30% |  |  |
Credit Facility [Member] | LIBOR Loans [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt instrument interest rate at period end |  |  |  |  | 1.25% | 1.25% |  |
Credit Facility [Member] | LIBOR Loans [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Leverage ratio |  |  |  |  | 1.00% |  |  |
Credit Facility [Member] | LIBOR Loans [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Leverage ratio |  |  |  |  | 1.75% |  |  |
Credit Facility [Member] | Base Rate Loans [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt instrument interest rate at period end |  |  |  |  | 0.25% | 0.25% |  |
Credit Facility [Member] | Base Rate Loans [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Leverage ratio |  |  |  |  | 0.00% |  |  |
Credit Facility [Member] | Base Rate Loans [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Leverage ratio |  |  |  |  | 0.75% |  |  |
Credit Facility [Member] | MUFG Union Bank, N.A [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Credit facility, maximum |  |  |  |  |  |  | $ 12,000,000.0 |
Revolving credit facility, maturity date |  |  |  |  | Mar. 31, 2025 |  |  |
Credit Facility [Member] | Treasury Sweep Note Due March 31, 2025 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Credit facility, indebtedness |  |  | 12,000,000.0 |  |  |  |  |
Revolving credit facility, maturity date |  |  |  |  | Mar. 31, 2025 |  |  |
Credit Facility [Member] | Notes Issued March 17, 2014 and Due March 17, 2021 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Revolving credit facility, maturity date |  |  |  |  | Mar. 17, 2021 |  |  |
Credit facility, aggregate outstanding principal |  |  | 40,000,000.0 |  |  |  |  |
Credit Facility [Member] | Notes Issued November 5, 2015 and Due November 5, 2022 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Revolving credit facility, maturity date |  |  |  |  | Nov. 05, 2022 |  |  |
Credit facility, aggregate outstanding principal |  |  | 60,000,000.0 |  |  |  |  |
Credit Facility [Member] | Sweep Service Facility [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Credit facility, maximum |  |  |  |  | $ 432,000,000.0 |  |  |
Credit facility, aggregate outstanding principal |  |  |  |  | 266,500,000 |  |  |
Unused commitment fees |  |  |  |  | $ 12,000,000.0 |  |  |
Credit Facility [Member] | One or More Tranches [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Revolving credit facility, available maximum borrowing capacity |  |  | 670,000,000.0 |  |  |  |  |
Letters of Credit [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Credit facility, maximum |  |  | 25,000,000.0 |  |  |  |  |
Swingline Loans [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Credit facility, maximum |  |  | 10,000,000.0 |  |  |  |  |
Unsecured revolving credit facility before Renewal [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Credit facility, maximum |  |  | $ 420,000,000.0 |  |  |  |  |
Unsecured revolving credit facility before Renewal [Member] | MUFG Union Bank, N.A [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Credit facility, maximum |  |  |  |  |  |  |  | $ 12,000,000.0

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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
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- Definition Date the credit facility terminates, in YYYY-MM-DD format. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition The cash inflow associated with the sale of a borrowing supported by a written promise to pay an obligation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3179-108585 + Details
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