Reserve for Known and Incurred but Not Reported Claims (Activity in Reserve for Known and Incurred but Not Reported Claims) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Insurance [Abstract]
Balance at beginning of year	$ 1,018,365	$ 976,462	$ 1,014,676
Provision related to current year	385,155	380,723	335,097
Provision related to prior years	64,868	149,633	62,620
Total Provision	450,023	530,356	397,717
Payments, net of recoveries, related to: Current year	196,656	182,653	160,138
Payments, net of recoveries, related to: Prior years	273,094	296,657	285,848
Total Payments, net of recoveries	469,750	479,310	445,986
Other	13,142	(9,143)	10,055
Balance at end of year	$ 1,011,780	$ 1,018,365	$ 976,462