Commitments and Contingencies - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified						3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Common Stock	Dec. 31, 2013 Common Stock	Mar. 31, 2014 Common Stock Energy Sector Business	Mar. 31, 2014 Claims Related to Events Before Business Divestiture
Commitments and Contingencies Disclosure [Line Items]
Indemnification obligation, expiration date						Jul. 31, 2016
Concentration of market risk related to available-for-sale securities	$ 2,637,802	$ 2,229,453	$ 2,637,800	$ 2,229,400	$ 588,600