Capital Stock - Schedule of Unamortized Value of Restricted Stock (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Amortization Expense [Line Items]
Total unamortized value	$ 1,232	$ 700	$ 400
1st quarter 2015 [Member]
Amortization Expense [Line Items]
Total unamortized value	201
2nd quarter 2015 [Member]
Amortization Expense [Line Items]
Total unamortized value	162
3rd quarter 2015 [Member]
Amortization Expense [Line Items]
Total unamortized value	162
4th quarter 2015 [Member]
Amortization Expense [Line Items]
Total unamortized value	162
1st quarter 2016 [Member]
Amortization Expense [Line Items]
Total unamortized value	154
2nd quarter 2016 [Member]
Amortization Expense [Line Items]
Total unamortized value	107
3rd quarter 2016 [Member]
Amortization Expense [Line Items]
Total unamortized value	107
4th quarter 2016 [Member]
Amortization Expense [Line Items]
Total unamortized value	107
1st quarter 2017 [Member]
Amortization Expense [Line Items]
Total unamortized value	$ 70