Fair Value - Presentation of Carrying Values and Fair Values of Certain of Company's Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Assets:
Investments, available-for-sale	$ 131,284	$ 130,248
Carrying Value [Member]
Assets:
Investments, available-for-sale	131,284	130,248
Limited partnership interests	9,053	7,513
Liabilities:
Debentures payable	40,321	40,301
Fair Value [Member]
Assets:
Investments, available-for-sale	131,284	130,248
Limited partnership interests	9,053	7,513
Liabilities:
Debentures payable	$ 18,412	$ 15,006