Investments - Schedule of Amortized Cost and Fair Value on Mortgage-Backed and Asset-Backed Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	$ 388,389	$ 355,052
Fair Value	385,870	354,440
Mortgage-backed securities [Member] | Agency [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	59,548	64,028
Fair Value	59,228	63,547
Mortgage-backed securities [Member] | Non Agency [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	3,110
Fair Value	3,063
Asset-backed securities [Member] | Auto Loans [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	14,862	14,816
Fair Value	14,884	14,841
Asset-backed securities [Member] | Credit Card Receivables [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	13,479	11,478
Fair Value	13,464	11,425
Asset-backed securities [Member] | Other Receivables [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	4,600	1,180
Fair Value	4,599	1,187
Mortgage-Backed and Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	95,599	91,502
Fair Value	$ 95,238	$ 91,000