Financial Guarantee Insurance Contracts - Summarized Future Gross Undiscounted Premiums Expected to be Collected, and Future Expected Premiums Earned, Net of Reinsurance (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014
Insurance [Abstract]
Future premiums expected to be collected, September 30, 2014	$ 39,988
Future premiums expected to be collected, December 31, 2014	31,037
Future premiums expected to be collected, December 31, 2015	123,705
Future premiums expected to be collected, December 31, 2016	116,974
Future premiums expected to be collected, December 31, 2017	110,511
Future premiums expected to be collected, December 31, 2018	105,182
Future premiums expected to be collected, December 31, 2023	466,339
Future premiums expected to be collected, December 31, 2028	370,487
Future premiums expected to be collected, December 31, 2033	237,081
Future premiums expected to be collected, December 31, 2038	92,686
Future premiums expected to be collected, December 31, 2043	30,826
Future premiums expected to be collected, December 31, 2048	12,538
Future premiums expected to be collected, December 31, 2053	2,252
Future premiums expected to be collected, December 31, 2058	31
Future premiums expected to be collected, Total	1,739,637
Future expected premiums to be earned, net of reinsurance, September 30, 2014	45,841
Future expected premiums to be earned, net of reinsurance, December 31, 2014	44,006
Future expected premiums to be earned, net of reinsurance, December 31, 2015	163,207
Future expected premiums to be earned, net of reinsurance, December 31, 2016	148,927
Future expected premiums to be earned, net of reinsurance, December 31, 2017	137,708
Future expected premiums to be earned, net of reinsurance, December 31, 2018	128,484
Future expected premiums to be earned, net of reinsurance, December 31, 2023	532,361
Future expected premiums to be earned, net of reinsurance, December 31, 2028	373,862
Future expected premiums to be earned, net of reinsurance, December 31, 2033	218,488
Future expected premiums to be earned, net of reinsurance, December 31, 2038	95,496
Future expected premiums to be earned, net of reinsurance, December 31, 2043	32,182
Future expected premiums to be earned, net of reinsurance, December 31, 2048	12,064
Future expected premiums to be earned, net of reinsurance, December 31, 2053	3,324
Future expected premiums to be earned, net of reinsurance, December 31, 2058	84
Future expected premiums to be earned, net of reinsurance, Total	$ 1,936,034