HBO led all television networks with 16 Writers Guild Awards nominations on Thursday, as its series "Game of Thrones," "Silicon Valley" and "True Detective" each earned multiple nods for honors writers bestow on their peers. Medieval fantasy "Game of Thrones," murder-mystery "True Detective," CBS's political drama "The Good Wife," Netflix's political thriller "House of Cards" and AMC's period portrait of the advertising world, "Mad Men," will each vie for the top award of best drama series.