Fair Value - Presentation of Carrying Values and Fair Values of Certain of Company's Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets:
Investments, available-for-sale	$ 135,428	$ 139,046
Carrying Value [Member]
Assets:
Investments, available-for-sale	135,428	139,046
Limited partnership interests	2,444
Liabilities:
Debentures payable	40,291	40,261
Fair Value [Member]
Assets:
Investments, available-for-sale	135,428	139,046
Limited partnership interests	2,444
Liabilities:
Debentures payable	$ 12,587	$ 12,723