Summary of Change in Fair Value of Level 3 Assets (Detail) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period		$ 70,208
Balance at end of period		90,970	$ 70,208
Limited partnership
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	[1]	2,116	4,086
Purchases		11,145
Sales		(2,516)	(252)
Changes in valuation	[2]	(368)	(1,718)
Net realized investment gains	[3]	(1)
Balance at end of period	[1]	10,376	2,116
Fixed maturity AFS securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	[1]	6,666	8,474
Change in unrealized losses	[4]	166	(376)
Purchases			1,999
Sales		(65)	(126)
Transfers into Level 3		1,947	2,049
Transfers out of Level 3		(1,954)	(5,354)
Balance at end of period	[1]	$ 6,760	$ 6,666

[1] Recorded as a component of limited partnerships and fixed maturity AFS securities in the Balance Sheets.

[2] Recorded as a component of net investment income in the Statements of Income.

[3] Recorded as a component of net realized investment gains (losses) for fixed maturity and net investment income for limited partnerships in the Statements of Income.

[4] Recorded as a component of Other Comprehensive Income (Loss) in net unrealized holding gains (losses) on AFS securities arising during the period.