Credit and Other Debt Agreements - Summary of Corporate and Other Debt (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Premium Financing Debt Facility [Member]
Debt Instrument [Line Items]
Periodic payments of interest and principal, expiry date	May 18, 2017	May 18, 2017
Fixed Rate of 6.44%, Balloon Due 2017 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	6.44%	6.44%
Principal payments, year due	2017	2017
Fixed Rate of 5.85%, $50.0 Million Due in 2016, 2018 and 2019 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	5.85%	5.85%
Long-Term debt maturities repayments in 2016	$ 50	$ 50
Long-Term debt maturities repayments in 2018	50	50
Long-Term debt maturities repayments in 2019	$ 50	$ 50
Fixed Rate of 2.80%, Balloon Due 2018 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	2.80%	2.80%
Principal payments, year due	2018	2018
Fixed Rate of 3.20%, Balloon Due 2019 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	3.20%	3.20%
Principal payments, year due	2019	2019
Fixed Rate of 3.99%, Balloon Due 2020 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	3.99%	3.99%
Principal payments, year due	2020	2020
Fixed Rate of 3.48%, Balloon Due 2020 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	3.48%	3.48%
Principal payments, year due	2020	2020
Fixed Rate of 5.18%, Balloon Due 2021 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	5.18%	5.18%
Principal payments, year due	2021	2021
Fixed rate of 3.69%, Balloon Due 2022 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	3.69%	3.69%
Principal payments, year due	2022	2022
Fixed Rate of 5.49%, Balloon Due 2023 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	5.49%	5.49%
Principal payments, year due	2023	2023
Fixed Rate of 4.13%, Balloon Due 2023 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	4.13%	4.13%
Principal payments, year due	2023	2023
Fixed Rate of 4.58% Balloon Due 2024 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	4.58%	4.58%
Principal payments, year due	2024	2024
Fixed Rate of 4.31%, Balloon Due 2025 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	4.31%	4.31%
Principal payments, year due	2025	2025
Fixed Rate of 4.73% Balloon Due 2026 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	4.73%	4.73%
Principal payments, year due	2026	2026
Fixed Rate of 4.36%, Balloon Due 2026 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	4.36%	4.36%
Principal payments, year due	2026	2026
Fixed Rate of 4.98% Balloon Due 2029 [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	4.98%	4.98%
Principal payments, year due	2029	2029
Prime or LIBOR plus up to 1.45%, expires September 19, 2018 [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	1.45%	1.45%
Periodic payments of interest and principal, expiry date	Sep. 19, 2018	Sep. 19, 2018
First Installment [Member] | Fixed Rate of 5.85%, $50.0 Million Due in 2016, 2018 and 2019 [Member]
Debt Instrument [Line Items]
Principal payments, year due	2016	2016
Second Installment [Member] | Fixed Rate of 5.85%, $50.0 Million Due in 2016, 2018 and 2019 [Member]
Debt Instrument [Line Items]
Principal payments, year due	2018	2018
Third Installment [Member] | Fixed Rate of 5.85%, $50.0 Million Due in 2016, 2018 and 2019 [Member]
Debt Instrument [Line Items]
Principal payments, year due	2019	2019
Facility B [Member] | Interbank rates plus 1.05%, Expires May 18, 2017 [Member] | Premium Financing Debt Facility [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	1.05%	1.05%
Facility C and D [Member] | Interbank rates plus 0.55%, Expires May 18, 2017 [Member] | Premium Financing Debt Facility [Member]
Debt Instrument [Line Items]
Periodic Payment of Interest	0.55%	0.55%