Fair Value Measurements - Changes in Life Expectancy Used to Estimate Fair Value (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Value	$ 457,810		$ 457,810		$ 388,886
Change in Value	0	$ 0	0	$ (426)
+6 Life Expectancy Months Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Value	384,990		384,990
Change in Value			(72,820)
-6 Life Expectancy Months Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Value	536,666		536,666
Change in Value			78,856
Red Falcon Trust
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Value	55,685		55,685
Change in Value			0
Red Falcon Trust | +6 Life Expectancy Months Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Value	53,734		53,734
Change in Value			(1,951)
Red Falcon Trust | -6 Life Expectancy Months Adjustment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Value	$ 57,236		57,236
Change in Value			$ 1,551