Credit and Other Debt Agreements - Summary of Debt (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Fixed Rate of 6.26%, Balloon Due 2014 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	6.26%	6.26%
Principal payments, year due	2014	2014
Fixed Rate of 6.44%, Balloon Due 2017 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	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]
Semi-annual payments of interest, fixed rate	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 5.18%, Balloon Due 2021 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	5.18%	5.18%
Principal payments, year due	2021	2021
Fixed Rate of 5.49%, Balloon Due 2023 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	5.49%	5.49%
Principal payments, year due	2023	2023
Fixed Rate of 3.99%, Balloon Due 2020 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	3.99%	3.99%
Principal payments, year due	2020	2020
Fixed rate of 3.69%, balloon due 2022 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	3.69%	3.69%
Principal payments, year due	2022	2022
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
Credit Agreement [Member] | Prime or LIBOR plus up to 1.45%, expires September 19, 2018 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	1.45%	1.45%
Periodic payments of interest and principal, expiry date	Sep. 19, 2018	Sep. 19, 2018