Investments - Schedule of Other Long-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Other long-term investments	$ 53,852	$ 38,438
Investment in limited partnerships
Investment [Line Items]
Other long-term investments	51,509	31,409
Low-income housing interests
Investment [Line Items]
Other long-term investments	0	3,767
Other
Investment [Line Items]
Other long-term investments	$ 2,343	$ 3,262