Investments - Aging of Gross Unrealized Investment Losses (Detail) $ in Thousands	Jun. 30, 2015 USD ($) Security	Dec. 31, 2014 USD ($) Security
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Number of Securities, Less Than Twelve Months | Security	803	214
Gross Unrealized Losses, Less Than Twelve Months	$ 4,421	$ 1,527
Fair Value, Less Than Twelve Months	$ 213,317	$ 111,109
Number of Securities, Twelve Months or Greater | Security	22	27
Gross Unrealized Losses, Twelve Months or Greater	$ 63	$ 114
Fair Value, Twelve Months or Greater	$ 1,268	$ 4,698
Fixed Maturity [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Number of Securities, Less Than Twelve Months | Security	415	212
Gross Unrealized Losses, Less Than Twelve Months	$ 2,504	$ 457
Fair Value, Less Than Twelve Months	$ 197,721	$ 98,765
Number of Securities, Twelve Months or Greater | Security	13	26
Gross Unrealized Losses, Twelve Months or Greater	$ 34	$ 92
Fair Value, Twelve Months or Greater	$ 1,011	$ 4,208
Equity Securities [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Number of Securities, Less Than Twelve Months | Security	388	2
Gross Unrealized Losses, Less Than Twelve Months	$ 1,917	$ 1,070
Fair Value, Less Than Twelve Months	$ 15,596	$ 12,344
Number of Securities, Twelve Months or Greater | Security	9	1
Gross Unrealized Losses, Twelve Months or Greater	$ 29	$ 22
Fair Value, Twelve Months or Greater	$ 257	$ 490
U.S. Government and Agency Securities [Member] | Fixed Maturity [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Number of Securities, Less Than Twelve Months | Security	22	11
Gross Unrealized Losses, Less Than Twelve Months	$ 503	$ 15
Fair Value, Less Than Twelve Months	$ 16,856	$ 2,451
Number of Securities, Twelve Months or Greater | Security		1
Gross Unrealized Losses, Twelve Months or Greater		$ 1
Fair Value, Twelve Months or Greater		$ 109
States, Municipalities and Political Subdivisions [Member] | Fixed Maturity [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Number of Securities, Less Than Twelve Months | Security	42	14
Gross Unrealized Losses, Less Than Twelve Months	$ 438	$ 15
Fair Value, Less Than Twelve Months	$ 31,251	$ 7,661
Number of Securities, Twelve Months or Greater | Security	1	1
Gross Unrealized Losses, Twelve Months or Greater	$ 4	$ 3
Fair Value, Twelve Months or Greater	$ 165	$ 177
Industrial And Commercial Bank Of China Financial Services Llc [Member] | Fixed Maturity [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Number of Securities, Less Than Twelve Months | Security	134	98
Gross Unrealized Losses, Less Than Twelve Months	$ 445	$ 204
Fair Value, Less Than Twelve Months	$ 56,080	$ 51,156
Number of Securities, Twelve Months or Greater | Security	3	10
Gross Unrealized Losses, Twelve Months or Greater	$ 20	$ 50
Fair Value, Twelve Months or Greater	$ 408	$ 1,975
Special Revenue [Member] | Fixed Maturity [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Number of Securities, Less Than Twelve Months | Security	164	71
Gross Unrealized Losses, Less Than Twelve Months	$ 1,091	$ 214
Fair Value, Less Than Twelve Months	$ 91,922	$ 36,643
Number of Securities, Twelve Months or Greater | Security	2	6
Gross Unrealized Losses, Twelve Months or Greater	$ 5	$ 23
Fair Value, Twelve Months or Greater	$ 336	$ 1,592
Redeemable Preferred Stocks [Member] | Fixed Maturity [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Number of Securities, Less Than Twelve Months | Security	53	18
Gross Unrealized Losses, Less Than Twelve Months	$ 27	$ 9
Fair Value, Less Than Twelve Months	$ 1,612	$ 854
Number of Securities, Twelve Months or Greater | Security	7	8
Gross Unrealized Losses, Twelve Months or Greater	$ 5	$ 15
Fair Value, Twelve Months or Greater	$ 102	$ 355
Nonredeemable Preferred Stocks [Member] | Equity Securities [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Number of Securities, Less Than Twelve Months | Security	227	1
Gross Unrealized Losses, Less Than Twelve Months	$ 101	$ 31
Fair Value, Less Than Twelve Months	$ 5,406	$ 2,552
Number of Securities, Twelve Months or Greater | Security	7	1
Gross Unrealized Losses, Twelve Months or Greater	$ 13	$ 22
Fair Value, Twelve Months or Greater	$ 225	$ 490
Equity Investment [Member] | Equity Securities [Member]
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Number of Securities, Less Than Twelve Months | Security	161	1
Gross Unrealized Losses, Less Than Twelve Months	$ 1,816	$ 1,039
Fair Value, Less Than Twelve Months	$ 10,190	$ 9,792
Number of Securities, Twelve Months or Greater | Security	2
Gross Unrealized Losses, Twelve Months or Greater	$ 16
Fair Value, Twelve Months or Greater	$ 32